Method for manufacturing solid-state imaging device

ABSTRACT

A solid-state imaging device having a light-receiving section that photoelectrically converts incident light includes an insulating film formed on a light-receiving surface of the light-receiving section and a film and having negative fixed charges formed on the insulating film. A hole accumulation layer is formed on a light-receiving surface side of the light-receiving section. A peripheral circuit section in which peripheral circuits are formed is provided on a side of the light-receiving section. The insulating film is formed between a surface of the peripheral circuit section and the film having negative fixed charges such that a distance from the surface of the peripheral circuit section to the film having negative fixed charges is larger than a distance from a surface of the light-receiving section to the film having negative fixed charges.

RELATED APPLICATION DATA

This application is a division of U.S. patent application Ser. No.12/339,941, filed Dec. 19, 2008, the entirety of which is incorporatedherein by reference to the extent permitted by law. The presentapplication claims the benefit of priority to Japanese PatentApplication No JP 2007-122370 and JP 2007-333691 filed in the JapanesePatent Office on May 7, 2007 and Dec. 26, 2007, respectively, theentirety both of which are incorporated by reference herein to theextent permitted by law.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a solid-state imaging device with thegeneration of dark currents suppressed, a manufacturing method for thesolid-state imaging device, and an imaging apparatus.

2. Description of the Related Art

In video cameras and digital still cameras, solid-state imaging devicesincluding CCD (Charge Coupled Device) or CMOS image sensors are widelyused. A reduction in noise as well as improvement of sensitivity is animportant object for all the solid-stage imaging devices.

Regardless of a state in which there is no incident light, i.e., a statein which there is no pure signal charge generated by photoelectricconversion of incident light, charges (electrons) caused bymicro-defects present in a substrate interface of a light-receivingsurface are captured as signals and change to micro-currents. Themicro-currents are detected as dark currents. Further, dark currents arecaused by a deep level defect existing in an interface between a Silayer and an insulating layer (interface state density). In particular,these dark currents are noise that should be reduced for a solid-stateimaging device.

As a method of suppressing the generation of the dark currents due tothe interface state density, for example, as shown in (2) in FIG. 54, anembedded photodiode structure having a hole accumulation layer 23including a P⁺ layer on a light-receiving section (e.g., a photodiode)12 as shown in (2) in FIG. 54 is used. In this specification, theembedded photodiode structure is referred to as HAD (Hole AccumulatedDiode) structure.

As shown in (1) in FIG. 54, in the structure in which the HAD structureis not provided, electrons due to interface state density flow into thephotodiode as dark currents.

On the other hand, as shown in (2) in FIG. 54, in the HAD structure, thegeneration of electrons from the interface is suppressed by the holeaccumulation layer 23 formed in the interface. Even if charges(electrons) are generated from the interface, since the charges(electrons) flow in the hole accumulation layers 23 of the P⁺ layer inwhich a large number of holes are present without flowing into a chargeaccumulation portion forming a well of potential in an N⁺ layer of thelight-receiving section 12, the charges (the electrons) can beeliminated.

Therefore, it is possible to prevent the charges due to the interfacefrom changing to dark currents to be detected and suppress the darkcurrents due to the interface state density.

As a method of forming the HAD structure, it is a general practice to,after ion-implanting impurities forming the P⁺ layer, for example, boron(B) or boron difluoride (BF₂) via a thermal oxide film or a CVD oxidefilm formed on a substrate, apply activation of the implanted impuritieswith annealing and form a P-type region near the interface.

However, heat treatment at high temperature equal to or higher than 700°C. is necessary and indispensable for activation of doping impurities.Therefore, it is difficult to form a hole accumulation layer by ionimplantation in a low-temperature process at low temperature equal to orlower than 400° C. Even when it is desired to avoid activation for longtime at high temperature in order to suppress the spread of a dopant,the method of forming a hole accumulation layer by applying the ionimplantation and the annealing is not preferable.

When silicon oxide or silicon nitride are formed on an upper layer of alight-receiving section by a method of low-temperature plasma CVD or thelike, compared with an interface between a film formed at hightemperature and a light-receiving surface, interface state density isdeteriorated. The deterioration in the interface state density causes anincrease in dark currents.

As described above, when it is desired to avoid the ion implantation andthe annealing at high temperature, it is difficult to perform formationof the hole accumulation layer by the ion implantation in the past.Moreover, the dark currents tend to worsen. To solve such a problem, itis necessary to form a hole accumulation layer with another method notdepending the ion implantation in the past.

For example, there is disclosed a technique for increasing the potentialof the surface of a photoelectric conversion section by embedding, in aninsulating layer made of silicon oxide on a photoelectric conversionelement having a conduction type opposite to a conduction type of asemiconductor region formed in the semiconductor region, chargeparticles having the opposite conduction type and the same polarity andforming an inversion layer on the surface to thereby prevent depletionof the surface and reduce the generation of dark currents (see, forexample, JP-A-1-256168).

However, in the technique, although a technique for embedding chargeparticles in the insulating layer is necessary, it is unclear what kindof embedding technique should be used. In general, in order to injectcharges into an insulating film from the outside as in a nonvolatilememory, an electrode for injecting charges is necessary. Even if chargescan be injected in a non-contact manner from the outside without usingthe electrode, in any case, the charges trapped in the insulating filmshould not be detrapped. A charge holding characteristic poses aproblem. Therefore, a high-quality insulating film with a high chargeholding characteristic is demanded but it is difficult to realize theinsulating film.

SUMMARY OF THE INVENTION

When it is attempted to form a sufficient hole accumulation layer byimplanting ions into a light-receiving section (a photoelectricconversion section) at high density, since the light-receiving sectionis damaged by the ion implantation, annealing at high temperature isnecessary but, in the annealing, spread of impurities occurs and aphotoelectric conversion characteristic is deteriorated.

On the other hand, when ion implantation is performed at lower densityin order to reduce the damage of the ion implantation, the density of ahole accumulation layer falls. The hole accumulation layer does not havea sufficient function of the hole accumulation layer.

In other words, it is difficult to achieve both the realization of asufficient hole accumulation layer and a reduction in dark currentswhile suppressing the spread of impurities and having a desiredphotoelectric conversion characteristic.

Therefore, it is desirable to achieve both the realization of thesufficient hole accumulation layer and the reduction in dark current.

According to an embodiment of the present invention, there is provided asolid-state imaging device (a first solid-state imaging device) having alight-receiving section that photoelectrically converts incident light.The solid-state imaging device has a film for reducing interface statedensity formed on a light-receiving surface of the light-receivingsection and a film having negative fixed charges formed on the film forreducing interface state density. A hole accumulation layer is formed onthe light-receiving surface side of the light-receiving section.

In the first solid-state imaging device, since the film having negativefixed charges is formed on the film for reducing interface statedensity, the hole accumulation layer is sufficiently formed in aninterface on the light-receiving surface side of the light-receivingsection by an electric field due to the negative fixed charges.Therefore, the generation of charges (electrons) from the interface issuppressed. Even if charges (electrons) are generated, since the chargesflows in the hole accumulation layer in which a large number of holesare present without flowing into a charge accumulation portion forming awell of potential in the light-receiving section, the charges (theelectrons) can be eliminated. Therefore, it is possible to prevent thecharges due to the interface from changing to dark currents to bedetected by the light-receiving section and suppress the dark currentsdue to the interface state density. Moreover, since the film forreducing interface state density is formed on the light-receivingsurface of the light-receiving section, the generation of electrons dueto the interface state density is further suppressed. Therefore, theelectrons due to the interface state density are prevented from flowinginto the light-receiving section as dark currents.

According to another embodiment of the present invention, there isprovided a solid-state imaging device (a second solid-state imagingdevice) having a light-receiving section that photoelectrically convertsincident light. The solid-state imaging device has an insulating filmthat is formed on a light-receiving surface of the light-receivingsection transmits the incident light and a film that is formed on theinsulating film and to which negative voltage is applied. A holeaccumulation layer is formed on the light-receiving surface side of thelight-receiving section.

In the second solid-state imaging device, since the film to whichnegative voltage is applied is formed on the insulating film formed onthe light-receiving surface of the light-receiving section, the holeaccumulation layer is sufficiently formed in an interface on thelight-receiving surface side of the light-receiving section by anelectric field generated when negative voltage is applied to the film towhich negative voltage is applied. Therefore, the generation of charges(electrons) from the interface is suppressed. Even if charges(electrons) are generated, since the charges flows in the holeaccumulation layer in which a large number of holes are present withoutflowing into a charge accumulation portion forming a well of potentialin the light-receiving section, the charges (the electrons) can beeliminated. Therefore, it is possible to prevent the charges due to theinterface from changing to dark currents to be detected by thelight-receiving section and suppress the dark currents due to theinterface state density.

According to still another embodiment of the present invention, there isprovided a solid-state imaging device (a third solid-state imagingdevice) having a light-receiving section that photoelectrically convertsincident light. The solid-state imaging device has an insulating filmformed on an upper layer on a light-receiving surface side of thelight-receiving section and a film that is formed on the insulating filmand has a value of a work function larger than that of an interface onthe light-receiving surface side of the light-receiving section thatphotoelectrically converts incident light.

In the third solid-state imaging device, the film having a value of awork function larger than that of the interface on the light-receivingsurface side of the light-receiving section that photoelectricallyconverts incident light is formed on the insulating film formed on thelight-receiving section. Therefore, hole accumulation in the interfaceon the light-receiving side of the light-receiving section is possible.Consequently, dark currents are reduced.

According to still another embodiment of the present invention, there isprovided a manufacturing method (a first manufacturing method) for asolid-state imaging device for forming, in a semiconductor substrate, alight-receiving section that photoelectrically converts incident light.The manufacturing method has a step of forming a film for reducinginterface state density on a semiconductor substrate in which thelight-receiving section is formed and a step of forming a film havingnegative fixed charges on the film for reducing interface state density.A hole accumulation layer is formed on the light-receiving surface sideof the light-receiving section by the film having negative fixedcharges.

In the manufacturing method (the first manufacturing method) for asolid-state imaging device, since the film having negative fixed chargesis formed on the film for reducing interface state density, the holeaccumulation layer is sufficiently formed in an interface on thelight-receiving surface side of the light-receiving section by anelectric field due to the negative fixed charges. Therefore, thegeneration of charges (electrons) from the interface is suppressed. Evenif charges (electrons) are generated, since the charges flows in thehole accumulation layer in which a large number of holes are presentwithout flowing into a charge accumulation portion forming a well ofpotential in the light-receiving section, the charges (the electrons)can be eliminated. Therefore, it is possible to prevent dark currentsgenerated by the charges due to the interface from being detected by thelight-receiving section and suppress the dark currents due to theinterface state density. Moreover, since the film for reducing interfacestate density is formed on the light-receiving surface of thelight-receiving section, the generation of electrons due to theinterface state density is further suppressed. Therefore, the electronsdue to the interface state density are prevented from flowing into thelight-receiving section as dark currents. Since the film having negativefixed charges is used, it is possible to form an HAD structure withoutapplying ion implantation and annealing thereto.

According to still another embodiment of the present invention, there isprovided a manufacturing method (a first manufacturing method) for asolid-state imaging device for forming, in a semiconductor substrate, alight-receiving section that photoelectrically converts incident light.The manufacturing method has a step of forming, on a light-receivingsurface of the light-receiving section, an insulating film thattransmits the incident light and a step of forming a film to whichnegative voltage on the insulating film. A hole accumulation layer isformed on the light-receiving surface side of the light-receivingsection by applying negative voltage to the film to which negativevoltage is applied.

In the manufacturing method for a solid-state imaging device (the secondmanufacturing method), since the film to which negative voltage isapplied is formed on the insulating film formed on the light-receivingsurface of the light-receiving section, the hole accumulation layer issufficiently formed in an interface on the light-receiving surface sideof the light-receiving section by an electric field generated whennegative voltage is applied to the film to which negative voltage isapplied. Therefore, the generation of charges (electrons) from theinterface is suppressed. Even if charges (electrons) are generated,since the charges flows in the hole accumulation layer in which a largenumber of holes are present without flowing into a charge accumulationportion forming a well of potential in the light-receiving section, thecharges (the electrons) can be eliminated. Therefore, it is possible toprevent dark currents generated by the charges due to the interface frombeing detected by the light-receiving section and suppress the darkcurrents due to the interface state density. Since the film havingnegative fixed charges is used, it is possible to form an HAD structurewithout applying ion implantation and annealing thereto.

According to still another embodiment of the present invention, there isprovided a manufacturing method for a solid-state imaging device (athird manufacturing method) for forming, in a semiconductor substrate, alight-receiving section that photoelectrically converts incident light.The manufacturing method has a step of forming an insulating film on anupper layer on a light-receiving surface side of the light-receivingsection and a step of forming, on the insulating film, a film having avalue of a work function larger than that of an interface on thelight-receiving surface side of the light-receiving section thatphotoelectrically converts incident light.

In the manufacturing method for a solid-state imaging device (the thirdmanufacturing method), the film having a value of a work function largerthan that of the interface on the light-receiving surface side of thelight-receiving section that photoelectrically converts incident lightis formed on the insulating film formed on the light-receiving section.Therefore, it is possible to form a hole accumulation layer in theinterface on the light-receiving side of the light-receiving section.Consequently, dark currents are reduced.

According to still another embodiment of the present invention, there isprovided an imaging apparatus (a first imaging apparatus) including acondensing optical unit that condenses incident light, a solid-stateimaging device that receives the incident light condensed by thecondensing optical unit and photoelectrically converts the incidentlight, and a signal processing unit that processesphotoelectrically-converted signal charges. The solid-state imagingdevice has a film for reducing interface state density formed on alight-receiving surface of a light-receiving section of the solid-stageimaging device that photoelectrically converts the incident light and afilm having negative fixed charges formed on the film for reducinginterface state density. A hole accumulation layer is formed on thelight-receiving surface of the light-receiving section.

In the first imaging apparatus, since the first solid-state imagingdevice is used, a solid-state imaging device with dark currents reducedis used.

According to still another embodiment of the present invention, there isprovided an imaging apparatus (a second imaging apparatus) including acondensing optical unit that condenses incident light, a solid-stateimaging device that receives the incident light condensed by thecondensing optical unit and photoelectrically converts the incidentlight, and a signal processing unit that processesphotoelectrically-converted signal charges. The solid-state imagingdevice has an insulating film formed on a light-receiving surface of alight-receiving section of the solid-state imaging device thatphotoelectrically converts the incident light and a film to whichnegative voltage is applied formed on the insulating film. Theinsulating film includes an insulating film that transmits the incidentfilm. A hole accumulation layer is formed on the light-receiving surfaceof the light-receiving section.

In the second imaging apparatus, since the second solid-state imagingdevice is used, a solid-state imaging device with dark currents reducedis used.

According to still another embodiment of the present invention, there isprovided an imaging apparatus (a third imaging apparatus) including acondensing optical unit that condenses incident light, a solid-stateimaging device that receives the incident light condensed by thecondensing optical unit and photoelectrically converts the incidentlight, and a signal processing unit that processesphotoelectrically-converted signal charges. The solid-state imagingdevice has an insulating film formed on an upper layer on alight-receiving surface side of a light-receiving section that convertsthe incident light into signal charges and a film that is formed on theinsulating film and has a value of a work function larger than that ofan interface on the light-receiving surface side of the light-receivingsection that photoelectrically converts incident light.

In the third imaging apparatus, since the third solid-state imagingdevice is used, a solid-state imaging device with dark currents reducedis used.

With the solid state imaging apparatuses according to the embodiments,since dark currents can be suppressed, noise in a picked-up image can bereduced. Therefore, there is an effect that it is possible to obtain ahigh-quality image. In particular, it is possible to reduce generationof white dots (dots of the primary colors in a color CCD) due to darkcurrents in long-time exposure with a small exposure amount.

With the manufacturing methods for a solid state imaging deviceaccording to the embodiments, since dark currents can be suppressed,noise in a picked-up image can be reduced. Therefore, there is an effectthat it is possible to realize a solid-state imaging device that canobtain a high-quality image. In particular, it is possible to realize asolid-state imaging device that can reduce generation of white dots(dots of the primary colors in a color CCD) due to dark currents inlong-time exposure with a small exposure amount.

With the imaging apparatus according to the embodiments, since thesolid-state imaging devices that can suppress dark current are used,noise in a picked-up image can be reduced. Therefore, there is an effectthat it is possible to record a high-definition video. In particular, itis possible to reduce generation of white dots (dots of the primarycolors in a color CCD) due to dark currents in long-time exposure with asmall exposure amount.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a main part configuration of a solid-stateimaging device (a first solid-state imaging device) according to a firstembodiment of the present invention;

FIG. 2 shows energy band diagrams for explaining an effect of thesolid-state imaging device (the first solid-state imaging device)according to the first embodiment;

FIG. 3 is a sectional view of a main part configuration of a solid-stateimaging device (a first solid-state imaging device) according to amodification of the first embodiment;

FIG. 4 is a sectional view of a main part configuration of a solid-stateimaging device according to another modification of the firstembodiment;

FIG. 5 is a sectional view of a main part configuration for explainingan action of negative fixed charges in the case in which a film havingnegative fixed charges is present near a peripheral circuit section;

FIG. 6 is a sectional view of a main part configuration of a solid-stateimaging device (a first solid-state imaging device) according to asecond embodiment of the present invention;

FIG. 7 is a sectional view of a main part configuration of a solid-stateimaging device (a first solid-state imaging device) according to a thirdembodiment of the present invention;

FIG. 8 shows sectional views of a manufacturing process of amanufacturing method (a first manufacturing method) for a solid-stageimaging device according to the first embodiment;

FIG. 9 shows sectional views of the manufacturing process of themanufacturing method (the first manufacturing method) for a solid-stateimaging device according to the first embodiment;

FIG. 10 is a sectional view of the manufacturing process of themanufacturing method (the first manufacturing method) for a solid-stateimaging device according to the first embodiment;

FIG. 11 shows sectional views of a manufacturing process of amanufacturing method (a first manufacturing method) for a solid-stateimaging device according to the second embodiment;

FIG. 12 shows sectional views of the manufacturing process of themanufacturing method (the first manufacturing method) for a solid-stateimaging device according to the second embodiment;

FIG. 13 is a sectional view of the manufacturing process of themanufacturing method (the first manufacturing method) for a solid-stateimaging device according to the second embodiment;

FIG. 14 shows sectional views of a manufacturing process of amanufacturing method (a first manufacturing method) for a solid-stateimaging device according to the third embodiment;

FIG. 15 shows sectional views of the manufacturing process of themanufacturing method (the first manufacturing method) for a solid-stateimaging device according to the third embodiment;

FIG. 16 is a sectional view of the manufacturing process of themanufacturing method (the first manufacturing method) for a solid-stateimaging device according to the third embodiment;

FIG. 17 shows sectional views of a manufacturing process of amanufacturing method (a first manufacturing method) for a solid-stateimaging device according to a fourth embodiment of the presentinvention;

FIG. 18 shows sectional views of the manufacturing processing of themanufacturing method (the first manufacturing method) for a solid-stateimaging device according to the fourth embodiment;

FIG. 19 is a sectional view of the manufacturing process of themanufacturing method (the first manufacturing method) for a solid-stateimaging device according to the fourth embodiment;

FIG. 20 shows sectional views of a manufacturing process of amanufacturing method for a solid-state imaging device according to afifth embodiment of the present invention;

FIG. 21 shows sectional views of the manufacturing process of themanufacturing method (the first manufacturing method) for a solid-stateimaging device according to the fifth embodiment;

FIG. 22 is a relational graph of flat band voltage and oxide filmequivalent thickness for explaining that negative fixed charges arepresent in a hafnium oxide (HfO₂) film;

FIG. 23 is a comparative graph of interface state density for explainingthat negative fixed charges are present in the hafnium oxide (HfO₂)film;

FIG. 24 is a relational chart of flat band voltage and oxide filmequivalent thickness for explaining formation of electrons and formationof holes relative to a thermal oxide film;

FIG. 25 shows sectional views of a manufacturing process of amanufacturing method (a first manufacturing method) for a solid-stateimaging device according to a sixth embodiment of the present invention;

FIG. 26 is a graph of a C-V (capacity-voltage) characteristic of asolid-state imaging device, in which a film having negative fixedcharges is used, manufactured by the manufacturing method according tothe sixth embodiment;

FIG. 27 is a graph of a C-V (capacity-voltage) characteristic of thesolid-state imaging device, in which the film having negative fixedcharges is used, manufactured by the first manufacturing methodaccording to the sixth embodiment;

FIG. 28 is a graph of a C-V (capacity-voltage) characteristic of thesolid-state imaging device, in which the film having negative fixedcharges is used, manufactured by the first manufacturing methodaccording to the sixth embodiment;

FIG. 29 shows sectional views of a manufacturing process of amanufacturing method (a first manufacturing method) for a solid-stateimaging device according to a seventh embodiment of the presentinvention;

FIG. 30 shows sectional views of the manufacturing process of themanufacturing method (the first manufacturing method) for a solid-stateimaging device according to the seventh embodiment;

FIG. 31 shows sectional views of the manufacturing process of themanufacturing method (the first manufacturing method) for a solid-stateimaging device according to the seventh embodiment;

FIG. 32 is a graph for explaining a dark current suppression effect of asolid-state imaging device, in which a film having negative fixingcharges is used, manufactured by the first manufacturing methodaccording to the seventh embodiment;

FIG. 33 shows sectional views of a manufacturing process of amanufacturing method (a first manufacturing method) for a solid-stateimaging device according to an eighth embodiment of the presentinvention;

FIG. 34 shows sectional views of the manufacturing process of themanufacturing method (the first manufacturing method) for a solid-stateimaging device according to the eighth embodiment;

FIG. 35 shows sectional views of the manufacturing process of themanufacturing method (the first manufacturing method) for a solid-stateimaging device according to the eighth embodiment;

FIG. 36 is a graph for explaining a dark current suppression effect of asolid-state imaging device, in which a film having negative fixingcharges is used, manufactured by the first manufacturing methodaccording to the eight embodiment;

FIG. 37 shows sectional views of a manufacturing step of a manufacturingmethod (a first manufacturing method) for a solid-state imaging deviceaccording to a ninth embodiment of the present invention;

FIG. 38 is a relational graph of temperature and depth relative to lightirradiation time;

FIG. 39 is a relational graph of temperature and depth relative to lightirradiation time;

FIG. 40 is a schematic sectional view for explaining an interferencecondition relative to a refractive index;

FIG. 41 is a sectional view of a main part configuration of asolid-state imaging device (a second solid-state imaging device)according to the first embodiment;

FIG. 42 is a sectional view of a main part configuration of asolid-state imaging device (a second solid-state imaging device)according to the second embodiment;

FIG. 43 shows sectional views of a manufacturing process of amanufacturing method (a second manufacturing method) for a solid-stateimaging device according to the first embodiment;

FIG. 44 shows sectional views of the manufacturing process of themanufacturing method (the second manufacturing method) for a solid-stateimaging device according to the first embodiment;

FIG. 45 is a sectional view of the manufacturing process of themanufacturing method (the second manufacturing method) for a solid-stateimaging device according to the first embodiment;

FIG. 46 shows sectional views of a manufacturing process of amanufacturing method (a second manufacturing method) for a solid-stateimaging device according to the second embodiment;

FIG. 47 shows sectional views of the manufacturing process of themanufacturing method (the second manufacturing method) for a solid-stateimaging device according to the second embodiment;

FIG. 48 is a sectional view of a main part configuration of asolid-state imaging device (a third solid-state imaging device)according to an embodiment of the present invention;

FIG. 49 is a sectional view of a main part configuration of an exampleof a configuration of a solid-state imaging device in which a holeaccumulation auxiliary film is used;

FIG. 50 is a flowchart of a manufacturing method (a third manufacturingmethod) for a solid-state imaging device according to an embodiment ofthe present invention;

FIG. 51 shows sectional views of a manufacturing process of themanufacturing method (the third manufacturing method) according to theembodiment;

FIG. 52 shows sectional views of a main part manufacturing process ofthe manufacturing method (the third manufacturing method) according tothe embodiment;

FIG. 53 is a block diagram of an imaging apparatus according to anembodiment of the present invention; and

FIG. 54 shows sectional views of a schematic structure of alight-receiving section for explaining a method of suppressinggeneration of dark currents due to interface state density.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A solid-state imaging device (a first solid-state imaging device)according to a first embodiment of the present invention is explainedbelow with reference to a sectional view of a main part configuration inFIG. 1.

As shown in FIG. 1, the solid-state imaging device 1 has, in asemiconductor substrate (or a semiconductor layer) 11, a light-emittingsection 12 that photoelectrically converts incident light L. Thesolid-state imaging device 1 has, on a side of the light-receivingsection 12, a peripheral circuit section 14 in which peripheral circuits(not specifically shown) are formed via a pixel separation area 13.

In the following explanation, the solid-state imaging device 1 has thelight-receiving section 12 in the semiconductor substrate 11.

A film 21 for reducing interface state density is formed on alight-receiving surface 12 s of the light-receiving section (including ahole accumulation layer 23 described later) 12. The film 21 for reducinginterface state density is formed by, for example, a silicon oxide(SiO₂) film. A film 22 having negative fixed charges is formed on thefilm 21 for reducing interface state density. Consequently, the holeaccumulation layer 23 is formed on the light-receiving surface side ofthe light-receiving section 12.

Therefore, at least on the light-receiving section 12, the film 21 forreducing interface state density is formed, by the film 22 havingnegative fixed charges, in thickness enough for forming the holeaccumulation layer 23 on the light-receiving surface 12 s side of thelight-receiving section 12. The film thickness is, for example, equal toor larger than one atom layer and equal to or smaller than 100 nm.

In the peripheral circuits of the peripheral circuit section 14, forexample, when the solid-state imaging device 1 is a CMOS image sensor,there is a pixel circuit including transistors such as a transfertransistor, a reset transistor, an amplification transistor, and aselection transistor.

The peripheral circuits include a driving circuit that performs anoperation for reading out a signal of a readout row of a pixel arraysection including plural light-receiving sections 12, a verticalscanning circuit that transfers the read-out signal, a shift register oran address decoder, and a horizontal scanning circuit as well.

In the peripheral circuits of the peripheral circuit section 14, forexample, when the solid-state imaging device 1 is a CCD image sensor,there are a readout gate that reads out photoelectrically-convertedsignal charges from the light-receiving section to a vertical transfergate, a vertical-charge transfer section that transfers the read-outsignal charges in a vertical direction. The peripheral circuits includea horizontal-charge transfer section as well.

The film 22 having negative fixed charges is formed by, for example, ahafnium oxide (HfO₂) film, an aluminum oxide (Al₂O₃) film, a zirconiumoxide (ZrO₂) film, a tantalum oxide (Ta₂O₅) film, or a titanium oxide(TiO₂) film. The films of the kinds described above are actually used ina gate insulating film and the like of an insulated-gate field-effecttransistor. Therefore, since a film forming method is established, it ispossible to easily form the films.

Examples of the film forming method include the chemical vapordeposition method, the sputtering method, and the atomic layerdeposition method. The atomic layer deposition method is suitably usedbecause an SiO₂ layer for reducing interface state density can besimultaneously formed by about 1 nm during the film formation.

Examples of materials other than the above include lanthanum oxide(La₂O₃), praseodymiumoxide (Pr₂O₃), cerium oxide (CeO₂), neodymium oxide(Nd₂O₃), promethium oxide (Pm₂O₃), samarium oxide (Sm₂O₃), europiumoxide (Eu₂O₃), gadolinium oxide (Gd₂O₃), terbium oxide (Tb₂O₃),dysprosium oxide (Dy₂O₃), holmium oxide (Ho₂O₃), erbium oxide (Er₂O₃),thulium oxide (Tm₂O₃), ytterbium oxide (Yb₂O₃), lutetium oxide (Lu₂O₃),and yttrium oxide (Y₂O₃).

The film 22 having negative fixed charges can be formed by a hafniumnitride film, an aluminum nitride film, a hafnium oxide nitride film, oran aluminum oxide nitride film as well.

Silicon (Si) or nitrogen (N) may be added to the film 22 having negativefixed charges as long as insulating properties thereof are not spoiled.The density of silicon or nitrogen is appropriately determined in arange in which the insulating properties of the film are not spoiled.However, in order to prevent an image defect such as white dotes frombeing caused, additives such as silicon or nitrogen is preferably addedto the surface of the film 22 having negative fixed charges, i.e., asurface on the opposite side of the light-receiving section 12 side.

Such addition of silicon (Si) or nitrogen (N) makes it possible toimprove heat resistance of the film and an ability of blocking ionimplantation in a process.

An insulating film 41 is formed on the film 22 having negative fixedcharges. A light shielding film 42 is formed on the insulating film 41above the peripheral circuit section 14. An area in which light does notenter is formed in the light-receiving section 12 by the light shieldingfilm 42. A black level in an image is determined by an output of thelight-receiving section 12.

Since light is prevented from entering the peripheral circuit section14, fluctuation in characteristics caused by the light entering theperipheral circuit section 14 is suppressed.

Moreover, an insulating film 43 having permeability to the incidentlight is formed. The surface of the insulating film 43 is preferablyplanarized.

Furthermore, a color filter layer 44 and a condensing lens 45 are formedon the insulating film 43.

In the solid-state imaging device (the first solid-state imaging device)1, the film 22 having negative fixed charges is formed on the film 21for reducing interface state density. Therefore, an electric field isapplied to the surface of the light-receiving section 12 via the film 21for reducing interface state density by the negative fixed charges inthe film 22 having negative fixed charges. The hole accumulation layer23 is formed on the surface of the light-receiving section 12.

As shown in (1) in FIG. 2, immediately after the film 22 having negativefixed charges is formed, the vicinity of the interface can be formed asthe hole accumulation layer 23 by the electric field, which is appliedby the negative fixed charges, present in the film.

Therefore, dark currents generated by the interface state density in theinterface between the light-receiving section 12 and the film 21 forreducing interface state density are suppressed. In other words, charges(electrons) generated from the interface are suppressed. Even if charges(electrons) are generated from the interface, since the charges (theelectrons) flow in the hole accumulation layer 23 in which a largenumber of holes are present without flowing into a charge accumulationportion forming a well of potential in the light-receiving section 12,the charges (the electrons) can be eliminated.

Therefore, it is possible to prevent dark currents generated by thecharges due to the interface from being detected by the light-receivingsection 12 and suppress the dark currents due to the interface statedensity.

On the other hand, as shown in (2) in FIG. 2, when a hole accumulationlayer is not provided, dark currents are generated by interface statedensity and flow into the light-receiving section 12.

As shown in (3) in FIG. 2, when the hole accumulation layer 23 is formedby ion implantation, as explained above, heat treatment at hightemperature equal to or higher than 700° C. is necessary andindispensable for activation of doping impurities in the ionimplantation. Therefore, spread of the impurities occurs, the holeaccumulation layer in the interface expands, and an area forphotoelectric conversion is narrowed. As a result, it is difficult toobtain desired photoelectric conversion characteristics.

In the solid-state imaging device 1, the film 21 for reducing interfacestate density is formed on the light-receiving surface 12 s of thelight-receiving section 12. Therefore, the generation of electrons dueto interface state density is further suppressed. This prevents theelectrons due to interface state density from flowing into thelight-receiving section 12 as dark currents.

When a hafnium oxide film is used as the film 22 having negative fixedcharges, since the refractive index of the hafnium oxide film is about2, it is possible not only to form a HAN structure by optimizing filmthickness but also to obtain a reflection prevention effect. When amaterial having a high refractive index is used other than the hafniumoxide film, it is possible to obtain the reflection prevention effect byoptimizing the film thickness of the material.

It is known that, when silicon oxide or silicon nitride, which is usedin the solid-state imaging device in the past, is formed at lowtemperature, fixed charges in a film are positive. It is difficult toform the HAD structure using the negative fixed charges.

A solid-state imaging device (a first solid-state imaging device)according to a modification of the embodiment is explained withreference to a sectional view of a main part configuration in FIG. 3.

As shown in FIG. 3, when the reflection prevention effect on thelight-receiving section 12 is insufficient only with the film 22 havingnegative fixed charges in the solid-state imaging device 1, in asolid-state imaging device 2, a reflection preventing film 46 is formedon the film 22 having negative fixed charges. The reflection preventingfilm 46 is formed by, for example, a silicon nitride film.

The insulating film 43 formed in the solid-state imaging device 1 is notformed.

Therefore, the color filter layer 44 and the condensing lens 45 areformed on the reflection preventing film 46.

It is possible to maximize the reflection prevention effect byadditionally forming the silicon nitride film in this way. Thisconfiguration can be applied to a solid-state imaging device 3 explainedbelow.

As explained above, since the reflection preventing film 46 is formed,reflection of light before the light is made incident on thelight-receiving section 12 can be reduced. Therefore, an amount ofincident light on the light-receiving section 12 can be increased. Thismakes it possible to improve the sensitivity of the solid-state imagingdevice 2.

A solid-state imaging device (a first solid-state imaging device)according to another modification of the embodiment is explained withreference to a sectional view of a main part configuration in FIG. 4.

As shown in FIG. 4, in a solid-state imaging device 3, the insulatingfilm 41 in the solid-state imaging device 1 is not formed. The lightshielding film 42 is directly formed on the film 22 having negativefixed charges. The insulating film 43 is not formed and the reflectionpreventing film 46 is formed.

Since the light shielding film 42 is directly formed on the film 22having negative fixed charges, the light shielding film 42 can be setcloser to the surface of the semiconductor substrate 11. Therefore, aspace between the light shielding film 42 and the semiconductorsubstrate 11 is narrowed. This makes it possible to reduce components oflight obliquely made incident from an upper layer of a neighboringlight-receiving section (photodiode), i.e., optical mixed colorcomponents.

When the film 22 having negative fixed charges is provided near theperipheral circuit section 14 as shown in FIG. 5, dark currents due tointerface state density on the surfaces of the light-receiving sections12 can be prevented by the hole accumulation layers 23 formed by thenegative fixed charges of the film 22 having negative fixed charges.

However, a potential difference is caused between the light-receivingsections 12 side and an element 14D present on the surface side. Anunexpected carrier flows into the element 14D on the surface side fromthe surfaces of the light-receiving sections 12 and causes a malfunctionof the peripheral circuit section 14.

Configurations for preventing such a malfunction are explained in secondand third embodiments of the present invention below.

A solid-state imaging device (a first solid-state imaging device)according to a second embodiment of the present invention is explainedwith reference to a sectional view of a main part configuration in FIG.6.

In FIG. 6, a light shielding film that shields a part of alight-receiving section and a peripheral circuit section, a color filterlayer that splits light made incident on the light-receiving section, acondensing lens that condenses the incident light on the light-receivingsection, and the like are not shown.

As shown in FIG. 6, in a solid-state imaging device 4, an insulatingfilm 24 is formed between the surface of the peripheral circuit section14 and the film 22 having negative fixed charges such that a distancefrom the surface of the peripheral circuit section 14 to the film 22 islarger than a distance from the surfaces of the light-receiving sections12 to the film 22 in the solid-state imaging device 1. When the film forreducing interface state density is formed by a silicon oxide film, theinsulating film 24 may be obtained by forming the film 21 for reducinginterface state density on the peripheral circuit section 14 thickerthan that on the light-receiving sections 12.

In this way, the insulating film 24 is formed between the surface of theperipheral circuit section 14 and the film 22 having negative fixedcharges such that the distance from the surface of the peripheralcircuit section 14 to the film 22 is larger than the distance from thesurfaces of the light-receiving sections 12 to the film 22. Therefore,the peripheral circuit section 14 is not affected by an electric fieldgenerated by the negative fixed charges in the film 22 having negativefixed charges.

Therefore, it is possible to prevent a malfunction of peripheralcircuits due to the negative fixed charges.

A solid-state imaging device (a first solid-state imaging device)according to a third embodiment of the present invention is explainedwith reference to a sectional view of a main part configuration in FIG.7.

In FIG. 7, a light shielding film that shields a part of alight-receiving section and a peripheral circuit section, a color filterlayer that splits light made incident on the light-receiving section, acondensing lens that condenses the incident light on the light-receivingsection, and the like are not shown.

As shown in FIG. 7, in a solid-state imaging device 5, a film 25 forseparating a film having negative fixed charges and a light-receivingsurface is formed between the peripheral circuit section 14 and the film22 having negative fixed charges in the solid-state imaging device 1.The film 25 desirably has positive fixed charges to cancel the influenceof the negative fixed charges. For example, silicon nitride ispreferably used for the film 25.

In this way, the film 25 having positive fixed charges is formed betweenthe peripheral circuit section 14 and the film 22 having negative fixedcharges. Therefore, the negative fixed charges of the film 22 havingnegative fixed charges are reduced by the positive fixed charges in thefilm 25. This prevents the peripheral circuit section 14 from beingaffected by the electric field of the negative fixed charges in the film22 having negative fixed charges.

Therefore, it is possible to prevent a malfunction of the peripheralcircuit section 14 due to the negative fixed charges.

The configuration in which the film 25 having positive fixed charges isformed between the peripheral circuit section 14 and the film 22 havingnegative fixed charges as described above can be applied to thesolid-state imaging devices 1, 2, 3, and 4 as well. Effects same asthose in the solid-state imaging device 5 can be obtained.

In the configuration on the film 22 having negative fixed charges in thesolid-state imaging devices 4 and 5, a light shielding film that shieldsa part of the light-receiving sections 12 and the peripheral circuitsection 14, a color filter layer that splits light made incident on atleast the light-receiving sections 12, a condensing lens that condensesthe incident light on the light-receiving sections 12, and the like areprovided. As an example, as the configuration, the configuration of anyone of the solid-state imaging devices 1, 2, and 3 can also be applied.

A manufacturing method (a first manufacturing method) for a solid-stateimaging device according to the first embodiment is explained withreference to sectional views of a manufacturing process showing a mainpart in FIG. 8 to FIG. 10. In FIG. 8 to FIG. 10, as an example, amanufacturing process for the solid-state imaging device 1 is shown.

As shown in (1) in FIG. 8, the light-receiving section 12 thatphotoelectrically converts incident light, the pixel separation areas 13that separate the light-receiving section 12, the peripheral circuitsection 14 in which peripheral circuits (not specifically shown) areformed with respect to the light-receiving section 12 via the pixelseparation area 13, and the like are formed in the semiconductorsubstrate (or the semiconductor layer) 11. An existing manufacturingmethod is used for the manufacturing method.

As shown in (2) in FIG. 8, the film 21 for reducing interface statedensity is formed on the light-receiving surface 12 s of thelight-receiving section 12, actually, on the semiconductor substrate 11.The film 21 for reducing interface state density is formed by, forexample, a silicon oxide (SiO₂) film.

The film 22 having negative fixed charges is formed on the film 21 forreducing interface state density. Consequently, the hole accumulationlayer 23 is formed on the light-receiving surface side of thelight-receiving section 12.

Therefore, at least on the light-receiving section 12, the film 21 forreducing interface state density needs to be formed, by the film 22having negative fixed charges, in thickness enough for forming the holeaccumulation layer 23 on the light-receiving surface 12 s side of thelight-receiving section 12. The film thickness is, for example, equal toor larger than one atom layer and equal to or smaller than 100 nm.

The film 22 having negative fixed charges is formed by, for example, ahafnium oxide (HfO₂) film, an aluminum oxide (Al₂O₃) film, a zirconiumoxide (ZrO₂) film, a tantalum oxide (Ta₂O₅) film, or a titanium oxide(TiO₂) film. The films of the kinds described above are actually used ina gate insulating film and the like of an insulated-gate field-effecttransistor. Therefore, since a film forming method is established, it ispossible to easily form the films. As the film forming method, forexample, the chemical vapor deposition method, the sputtering method,and the atomic layer deposition method can be used. The atomic layerdeposition method is suitably used because an SiO₂ layer for reducinginterface state density can be simultaneously formed by about 1 nmduring the film formation.

As materials other than the above, lanthanum oxide (La₂O₃), praseodymiumoxide (Pr₂O₃), cerium oxide (CeO₂), neodymium oxide (Nd₂O₃), promethiumoxide (Pm₂O₃), samarium oxide (Sm₂O₃), europium oxide (Eu₂O₃),gadolinium oxide (Gd₂O₃), terbium oxide (Tb₂O₃), dysprosium oxide(Dy₂O₃), holmium oxide (Ho₂O₃), erbium oxide (Er₂O₃), thulium oxide(Tm₂O₃), ytterbium oxide (Yb₂O₃), lutetium oxide (Lu₂O₃), yttrium oxide(Y₂O₃), and the like can be used. The film 22 having negative fixedcharges can be formed by a hafnium nitride film, an aluminum nitridefilm, a hafnium oxide nitride film, or an aluminum oxide nitride film aswell. These films also can be formed, for example, by the chemical vapordeposition, the sputtering method, and the atomic layer depositionmethod.

Silicon (Si) or nitrogen (N) may be added to the film 22 having negativefixed charges as long as insulating properties thereof are not spoiled.The density of silicon or nitrogen is appropriately determined in arange in which the insulating properties of the film are not spoiled.Such addition of silicon (Si) or nitrogen (N) makes it possible toimprove heat resistance of the film and an ability of blocking ionimplantation in a process.

When the film 22 having negative fixed charges is formed by a hafniumoxide (HfO₂) film, since the refractive index of the hafnium oxide film(HfO₂) is about 2, it is possible to efficiently obtain a reflectionprevention effect by adjusting the film thickness. Naturally, when otherkinds of films are used, it is possible to obtain the reflectionprevention effect by optimizing film thickness according to a refractiveindex.

The insulating film 41 is formed on the film 22 having negative fixedcharges. The light shielding film 42 is formed on the insulating film41. The insulating film 41 is formed by, for example, a silicon oxidefilm. The light shielding film 42 is formed by, for example, a metalfilm having light shielding properties.

The light shielding film 42 is formed on the film 22 having negativefixed charges via the insulating film 41 in this way. This makes itpossible to prevent a reaction of the film 22 having negative fixedcharges formed by a hafnium oxide film or the like and the metal of thelight shielding film 42.

When the light shielding film 42 is etched, since the insulating film 41functions as an etching stopper, it is possible to prevent etchingdamage to the film 22 having negative fixed charges.

As shown in (3) in FIG. 9, a resist mask (not shown) is formed on thelight shielding film 42 above a part of the light-receiving section 12and the peripheral circuit section 14 by the resist application and thelithography technique. The light shielding film 42 is etched by usingthe resist mask to leave the light shielding film 42 on the insulatingfilm 41 above a part of the light-receiving section 12 and theperipheral circuit section 14.

An area in which light does not enter is formed in the light-receivingsection 12 by the light shielding film 42. A black level in an image isdetermined by an output of the light receiving section 12.

Since light is prevented from entering the peripheral circuit section14, fluctuation in characteristics caused by the light entering theperipheral circuit section 14 is suppressed.

As shown in (4) in FIG. 9, the insulating film 43 that reduces a stepformed by the light shielding film 42 is formed on the insulating film41. The insulating film 43 is preferably planarized on the surfacethereof and is formed by, for example, a coated insulating film.

As shown in FIG. 10, the color filter layer 44 is formed on theinsulating film 43 above the light-receiving section 12 by an existingmanufacturing technique. The condensing lens 45 is formed on the colorfiler layer 44. A light transmissive insulating film (not shown) may beformed between the color filter layer 44 and the condensing lens 45 inorder to prevent machining damage to the color filter layer 44 in lensmachining.

The solid-state imaging device 1 is formed in this way.

In the manufacturing method (the first manufacturing method) for asolid-state imaging device according to the first embodiment, the film22 having negative fixed charges is formed on the film 21 for reducinginterface state density. Therefore, the hole accumulation layer 23 issufficiently formed in the interface on the light-receiving surface sideof the light-receiving section 12 by an electric field due to thenegative fixed charges in the film 22 having negative fixed charges.

Therefore, charges (electrons) generated from the interface aresuppressed. Even if charges (electrons) are generated, since the charges(electrons) flow in the hole accumulation layer 23 in which a largenumber of holes are present without flowing into a charge accumulationportion forming a well of potential in the light-receiving section 12,the charges (the electrons) can be eliminated.

Therefore, it is possible to prevent dark currents generated by thecharges due to the interface from being detected by the light-receivingsection and suppress the dark currents due to the interface statedensity.

Moreover, since the film 21 for reducing interface state density isformed on the light-receiving surface of the light-receiving section 12,the generation of electrons due to the interface state density isfurther suppressed. Therefore, the electrons due to the interface statedensity are prevented from flowing into the light-receiving section 12as dark currents. Since the film 22 having negative fixed charges isused, it is possible to form an HAD structure without applying ionimplantation and annealing thereto.

A manufacturing method (a first manufacturing method) for a solid-stateimaging device according to the second embodiment is explained withreference to sectional views of a manufacturing process showing a mainpart in FIG. 11 to FIG. 13. In FIG. 11 to FIG. 13, as an example, amanufacturing process for the solid-state imaging device 2 is shown.

As shown in (1) in FIG. 11, the light-receiving section 12 thatphotoelectrically converts incident light, the pixel separation areas 13that separate the light-receiving section 12, the peripheral circuitsection 14 in which peripheral circuits (not specifically shown) areformed with respect to the light-receiving section 12 via the pixelseparation area 13, and the like are formed in the semiconductorsubstrate (or the semiconductor layer) 11. An existing manufacturingmethod is used for the manufacturing method.

As shown in (2) in FIG. 11, the film 21 for reducing interface statedensity is formed on the light-receiving surface 12 s of thelight-receiving section 12, actually, on the semiconductor substrate 11.The film 21 for reducing interface state density is formed by, forexample, a silicon oxide (SiO₂) film. The film 22 having negative fixedcharges is formed on the film 21 for reducing interface state density.Consequently, the hole accumulation layer 23 is formed on thelight-receiving surface side of the light-receiving section 12.

Therefore, at least on the light-receiving section 12, the film 21 forreducing interface state density needs to be formed, by the film 22having negative fixed charges, in thickness enough for forming the holeaccumulation layer 23 on the light-receiving surface 12 s side of thelight-receiving section 12. The film thickness is, for example, equal toor larger than one atom layer and equal to or smaller than 100 nm.

The film 22 having negative fixed charges is formed by, for example, ahafnium oxide (HfO₂) film, an aluminum oxide (Al₂O₃) film, a zirconiumoxide (ZrO₂) film, a tantalum oxide (Ta₂O₅) film, or a titanium oxide(TiO₂) film.

The films of the kinds described above are actually used in a gateinsulating film and the like of an insulated-gate field-effecttransistor. Therefore, since a film forming method is established, it ispossible to easily form the films. As the film forming method, forexample, the chemical vapor deposition method, the sputtering method,and the atomic layer deposition method can be used.

As materials other than the above, lanthanum oxide (La₂O₃), praseodymiumoxide (Pr₂O₃), cerium oxide (CeO₂), neodymium oxide (Nd₂O₃), promethiumoxide (Pm₂O₃), samarium oxide (Sm₂O₃), europium oxide (Eu₂O₃),gadolinium oxide (Gd₂O₃), terbium oxide (Tb₂O₃), dysprosium oxide(Dy₂O₃), holmium oxide (Ho₂O₃), erbium oxide (Er₂O₃), thulium oxide(Tm₂O₃), ytterbium oxide (Yb₂O₃), lutetium oxide (Lu₂O₃), yttrium oxide(Y₂O₃), and the like can be used. The film 22 having negative fixedcharges can be formed by a hafnium nitride film, an aluminum nitridefilm, a hafnium oxide nitride film, or an aluminum oxide nitride film aswell. These films can also be formed by, for example, the chemical vapordeposition method, the sputtering method, and the atomic layerdeposition method. The atomic layer deposition method is suitably usedbecause an SiO₂ layer for reducing interface state density can besimultaneously formed by about 1 nm during the film formation.

Silicon (Si) or nitrogen (N) may be added to the film 22 having negativefixed charges as long as insulating properties thereof are not spoiled.The density of silicon or nitrogen is appropriately determined in arange in which the insulating properties of the film are not spoiled.Such addition of silicon (Si) or nitrogen (N) makes it possible toimprove heat resistance of the film and an ability of blocking ionimplantation in a process.

When the film 22 having negative fixed charges is formed by a hafniumoxide (HfO₂) film, since the refractive index of the hafnium oxide film(HfO₂) is about 2, it is possible to efficiently obtain a reflectionprevention effect by adjusting the film thickness. Naturally, when otherkinds of films are used, it is possible to obtain the reflectionprevention effect by optimizing film thickness according to a refractiveindex.

The insulating film 41 is formed on the film 22 having negative fixedcharges. The light shielding film 42 is formed on the insulating film41. The insulating film 41 is formed by, for example, a silicon oxidefilm. The light shielding film 42 is formed by, for example, a metalfilm having light shielding properties.

The light shielding film 42 is formed on the film 22 having negativefixed charges via the insulating film 41 in this way. This makes itpossible to prevent a reaction of the film 22 having negative fixedcharges formed by a hafnium oxide film or the like and the metal of thelight shielding film 42.

When the light shielding film 42 is etched, since the insulating film 41functions as an etching stopper, it is possible to prevent etchingdamage to the film 22 having negative fixed charges.

As shown in (3) in FIG. 12, a resist mask (not shown) is formed on thelight shielding film 42 above a part of the light-receiving section 12and the peripheral circuit section 14 by the resist application and thelithography technique. The light shielding film 42 is etched by usingthe resist mask to leave the light shielding film 42 on the insulatingfilm 41 above a part of the light-receiving section 12 and theperipheral circuit section 14. An area in which light does not enter isformed in the light-receiving section 12 by the light shielding film 42.A black level in an image is determined by an output of the lightreceiving section 12. Since light is prevented from entering theperipheral circuit section 14, fluctuation in characteristics caused bythe light entering the peripheral circuit section 14 is suppressed.

As shown in (4) in FIG. 12, the reflection preventing film 46 is formedon the insulating film 41 to cover the light shielding film 42. Thereflection preventing film 46 is formed by, for example, a siliconnitride film, the refractive index of which is about 2.

As shown in FIG. 13, the color filter layer 44 is formed on thereflection preventing film 46 above the light-receiving section 12 by anexisting manufacturing technique. The condensing lens 45 is formed onthe color filer layer 44. A light transmissive insulating film (notshown) may be formed between the color filter layer 44 and thecondensing lens 45 in order to prevent machining damage to the colorfilter layer 44 in lens machining.

The solid-state imaging device 2 is formed in this way.

In the manufacturing method (the first manufacturing method) for asolid-state imaging device according to the second embodiment, effectssame as those in the first embodiment are obtained.

Since the reflection preventing film 46 is formed, reflection of lightbefore the light is made incident on the light-receiving section 12 canbe reduced. Therefore, an amount of incident light on thelight-receiving section 12 can be increased. This makes it possible toimprove the sensitivity of the solid-state imaging device 2.

A manufacturing method (a first manufacturing method) for a solid-stateimaging device according to the third embodiment is explained withreference to sectional views of a manufacturing process showing a mainpart in FIG. 14 to FIG. 16. In FIG. 14 to FIG. 16, as an example, amanufacturing method for the solid-state imaging device 3 is shown.

As shown in (1) in FIG. 14, the light-receiving section 12 thatphotoelectrically converts incident light, the pixel separation areas 13that separate the light-receiving section 12, the peripheral circuitsection 14 in which peripheral circuits (not specifically shown) areformed with respect to the light-receiving section 12 via the pixelseparation area 13, and the like are formed in the semiconductorsubstrate (or the semiconductor layer) 11. An existing manufacturingmethod is used for the manufacturing method.

As shown in (2) in FIG. 14, the film 21 for reducing interface statedensity is formed on the light-receiving surface 12 s of thelight-receiving section 12, actually, on the semiconductor substrate 11.The film 21 for reducing interface state density is formed by, forexample, a silicon oxide (SiO₂) film.

The film 22 having negative fixed charges is formed on the film 21 forreducing interface state density. Consequently, the hole accumulationlayer 23 is formed on the light-receiving surface side of thelight-receiving section 12.

Therefore, at least on the light-receiving section 12, the film 21 forreducing interface state density needs to be formed, by the film 22having negative fixed charges, in thickness enough for forming the holeaccumulation layer 23 on the light-receiving surface 12 s side of thelight-receiving section 12. The film thickness is, for example, equal toor larger than one atom layer and equal to or smaller than 100 nm.

The film 22 having negative fixed charges is formed by, for example, ahafnium oxide (HfO₂) film, an aluminum oxide (Al₂O₃) film, a zirconiumoxide (ZrO₂) film, a tantalum oxide (Ta₂O₅) film, or a titanium oxide(TiO₂) film. The films of the kinds described above are actually used ina gate insulating film and the like of an insulated-gate field-effecttransistor. Therefore, since a film forming method is established, it ispossible to easily form the films. As the film forming method, forexample, the chemical vapor deposition method, the sputtering method,and the atomic layer deposition method can be used. The atomic layerdeposition method is suitably used because an SiO₂ layer for reducinginterface state density can be simultaneously formed by about 1 nmduring the film formation.

As materials other than the above, lanthanum oxide (La₂O₃), praseodymiumoxide (Pr₂O₃), cerium oxide (CeO₂), neodymium oxide (Nd₂O₃), promethiumoxide (Pm₂O₃), samarium oxide (Sm₂O₃), europium oxide (Eu₂O₃),gadolinium oxide (Gd₂O₃), terbium oxide (Tb₂O₃), dysprosium oxide(Dy₂O₃), holmium oxide (Ho₂O₃), erbium oxide (Er₂O₃), thulium oxide(Tm₂O₃), ytterbium oxide (Yb₂O₃), lutetium oxide (Lu₂O₃), yttrium oxide(Y₂O₃), and the like can be used. The film 22 having negative fixedcharges can be formed by a hafnium nitride film, an aluminum nitridefilm, a hafnium oxide nitride film, or an aluminum oxide nitride film aswell. These films can also be formed by, for example, the chemical vapordeposition method, the sputtering method, and the atomic layerdeposition method.

Silicon (Si) or nitrogen (N) may be added to the film 22 having negativefixed charges as long as insulating properties thereof are not spoiled.The density of silicon or nitrogen is appropriately determined in arange in which the insulating properties of the film are not spoiled.Such addition of silicon (Si) or nitrogen (N) makes it possible toimprove heat resistance of the film and an ability of blocking ionimplantation in a process.

When the film 22 having negative fixed charges is formed by a hafniumoxide (HfO₂) film, it is possible to efficiently obtain a reflectionprevention effect by adjusting the film thickness of the hafnium oxidefilm (HfO₂). Naturally, when other kinds of films are used, it ispossible to obtain the reflection prevention effect by optimizing filmthickness according to a refractive index.

The light shielding film 42 is formed on the film 22 having negativefixed charges. The light shielding film 42 is formed by, for example, ametal film having light shielding properties.

The light shielding film 42 is directly formed on the film 22 havingnegative fixed charges in this way. Therefore, since the light shieldingfilm 42 can be set closer to the surface of the semiconductor substrate11, a space between the light shielding film 42 and the semiconductorsubstrate 11 is narrowed. This makes it possible to reduce components oflight obliquely made incident from an upper layer of a neighboringlight-receiving section (photodiode), i.e., optical mixed colorcomponents.

As shown in (3) in FIG. 15, a resist mask (not shown) is formed on thelight shielding film 42 above a part of the light-receiving section 12and the peripheral circuit section 14 by the resist application and thelithography technique. The light shielding film 42 is etched by usingthe resist mask to leave the light shielding film 42 on the film 22having negative fixed charges above a part of the light-receivingsection 12 and the peripheral circuit section 14.

An area in which light does not enter is formed in the light-receivingsection 12 by the light shielding film 42. A black level in an image isdetermined by an output of the light receiving section 12.

Since light is prevented from entering the peripheral circuit section14, fluctuation in characteristics caused by the light entering theperipheral circuit section 14 is suppressed.

As shown in (4) in FIG. 15, the reflection preventing film 46 is formedon the film 22 having negative fixed charges to cover the lightshielding film 42. The reflection preventing film 46 is formed by, forexample, a silicon nitride film, the refractive index of which is about2.

As shown in FIG. 16, the color filter layer 44 is formed on thereflection preventing film 46 above the light-receiving section 12 by anexisting manufacturing technique.

The condensing lens 45 is formed on the color filer layer 44. A lighttransmissive insulating film (not shown) may be formed between the colorfilter layer 44 and the condensing lens 45 in order to prevent machiningdamage to the color filter layer 44 in lens machining.

The solid-state imaging device 3 is formed in this way.

In the manufacturing method (the first manufacturing method) for asolid-state imaging device according to the third embodiment, effectssame as those in the first embodiment are obtained. Since the lightshielding film 42 is directly formed on the film 22 having negativefixed charges, the light shielding film 42 can be set closer to thesurface of the semiconductor substrate 11. Therefore, a space betweenthe light shielding film 42 and the semiconductor substrate 11 isnarrowed. This makes it possible to reduce components of light obliquelymade incident from an upper layer of a neighboring light-receivingsection (photodiode), i.e., optical mixed color components.

Since the reflection preventing film 46 is formed, when the reflectionprevention effect is insufficient only with the film 22 having negativefixed charges, it is possible to maximize the reflection preventioneffect.

A manufacturing method (a first manufacturing method) according to afourth embodiment of the present invention is explained with referenceto sectional views of a manufacturing process showing a main part inFIG. 17 to FIG. 19. In FIG. 17 to FIG. 19, as an example, amanufacturing process for the solid-state imaging device 4 is shown.

As shown in (1) in FIG. 17, the light-receiving sections 12 thatphotoelectrically convert incident light, the pixel separation areas 13that separate the light-receiving sections 12, the peripheral circuitsection 14 in which peripheral circuits (e.g., a circuit 14C) are formedwith respect to the light-receiving section 12 via the pixel separationarea 13, and the like are formed in the semiconductor substrate (or thesemiconductor layer) 11. An existing manufacturing method is used forthe manufacturing method.

An insulating film 26 having permeability to the incident light isformed. The insulating film 26 is formed by, for example, a siliconoxide film.

As shown in (2) in FIG. 17, a resist mask 51 is formed on the insulatingfilm 26 above the peripheral circuit section 14 by the resistapplication and the lithography technique.

As shown in (3) in FIG. 18, the insulating film 26 is etched by usingthe resist mask 51 (see (2) in FIG. 17) to leave the insulating film 26on the peripheral circuit section 14.

Thereafter, the resist mask 51 is removed.

As shown in (4) in FIG. 18, the film 21 for reducing interface statedensity that covers the insulating film 26 is formed on thelight-receiving surfaces 12 s of the light-receiving sections 12,actually, on the semiconductor substrate 11. The film 21 for reducinginterface state density is formed by, for example, a silicon oxide(SiO₂) film.

As shown in FIG. 19, the film 22 having negative fixed charges is formedon the film 21 for reducing interface state density. Consequently, thehole accumulation layers 23 are formed on the light-receiving surfacesside of the light-receiving sections 12.

Therefore, at least on the light-receiving sections 12, the film 21 forreducing interface state density needs to be formed, by the film 22having negative fixed charges, in thickness enough for forming the holeaccumulation layers 23 on the light-receiving surfaces 12 s side of thelight-receiving sections 12. The film thickness is, for example, equalto or larger than one atom layer and equal to or smaller than 100 nm.

The film 22 having negative fixed charges is formed by, for example, ahafnium oxide (HfO₂) film, an aluminum oxide (Al₂O₃) film, a zirconiumoxide (ZrO₂) film, a tantalum oxide (Ta₂O₅) film, or a titanium oxide(TiO₂) film. The films of the kinds described above are actually used ina gate insulating film and the like of an insulated-gate field-effecttransistor. Therefore, since a film forming method is established, it ispossible to easily form the films. As the film forming method, forexample, the chemical vapor deposition method, the sputtering method,and the atomic layer deposition method can be used. The atomic layerdeposition method is suitably used because a silicon oxide (SiO₂) layerfor reducing interface state density can be simultaneously formed byabout 1 nm during the film formation.

As materials other than the above, lanthanum oxide (La₂O₃), praseodymiumoxide (Pr₂O₃), cerium oxide (CeO₂), neodymium oxide (Nd₂O₃), promethiumoxide (Pm₂O₃), samarium oxide (Sm₂O₃), europium oxide (Eu₂O₃),gadolinium oxide (Gd₂O₃), terbium oxide (Tb₂O₃), dysprosium oxide(Dy₂O₃), holmium oxide (Ho₂O₃), erbium oxide (Er₂O₃), thulium oxide(Tm₂O₃), ytterbium oxide (Yb₂O₃), lutetium oxide (Lu₂O₃), yttrium oxide(Y₂O₃), and the like can be used. The film 22 having negative fixedcharges can be formed by a hafnium nitride film, an aluminum nitridefilm, a hafnium oxide nitride film, or an aluminum oxide nitride film aswell. These films can also be formed by, for example, the chemical vapordeposition method, the sputtering method, and the atomic layerdeposition method.

Silicon (Si) or nitrogen (N) may be added to the film 22 having negativefixed charges as long as insulating properties thereof are not spoiled.The density of silicon or nitrogen is appropriately determined in arange in which the insulating properties of the film are not spoiled.Such addition of silicon (Si) or nitrogen (N) makes it possible toimprove heat resistance of the film and an ability of blocking ionimplantation in a process.

When the film 22 having negative fixed charges is formed by a hafniumoxide (HfO₂) film, since the refractive index of the hafnium oxide film(HfO₂) is about 2, it is possible to efficiently obtain a reflectionprevention effect by adjusting the film thickness. Naturally, when otherkinds of films are used, it is possible to obtain the reflectionprevention effect by optimizing film thickness according to a refractiveindex.

In the configuration on the film 22 having negative fixed charges in thesolid-state imaging device 4, a light shielding film that shields a partof the light-receiving sections 12 and the peripheral circuit section14, a color filter layer that splits light made incident on at least thelight-receiving sections 12, a condensing lens that condenses theincident light on the light-receiving sections 12, and the like areprovided. As an example, as the configuration, the configuration of anyone of the solid-state imaging devices 1, 2, and 3 can also be applied.

In the manufacturing method (the first manufacturing method) for asolid-state imaging device according to the fourth embodiment, the film22 having negative fixed charges is formed on the film 21 for reducinginterface state density. Therefore, the hole accumulation layers 23 aresufficiently formed in the interfaces on the light-receiving surfacesside of the light-receiving sections 12 by an electric field due to thenegative fixed charges in the film 22 having negative fixed charges.

Therefore, charges (electrons) generated from the interface can besuppressed. Even if charges (electrons) are generated, since the charges(electrons) flow in the hole accumulation layers 23 in which a largenumber of holes are present without flowing into charge accumulationportions forming wells of potential in the light-receiving sections 12,the charges (the electrons) can be eliminated.

Therefore, it is possible to prevent dark currents generated by thecharges due to the interface from being detected by the light-receivingsections and suppress the dark currents due to the interface statedensity. Further, since the film 21 for reducing interface state densityis formed on the light-receiving surfaces of the light-receivingsections 12, the generation of electrons due to the interface statedensity is further suppressed. Therefore, the electrons due to theinterface state density are prevented from flowing into thelight-receiving sections 12 as dark currents. Since the film 22 havingnegative fixed charges is used, it is possible to form an HAD structurewithout applying ion implantation and annealing thereto.

Moreover, since the insulating film 26 is formed on the peripheralcircuit section 14, a distance to the film 22 having negative fixedcharges on the peripheral circuit section 14 is longer than a distanceto the film 22 having negative fixed chares on the light-receivingsections 12. Therefore, a negative electric field applied to theperipheral circuit section 14 from the film 22 having negative fixedcharges is relaxed. In other words, since the influence of the film 22having negative fixed charges on the peripheral circuit section 14 isreduced, a malfunction of the peripheral circuit section 14 due to thenegative electric field by the film 22 having negative fixed charges isprevented.

A manufacturing method (a first manufacturing method) for a solid-stateimaging device according to a fifth embodiment of the present inventionis explained with reference to sectional views of a manufacturingprocess showing a main part in FIG. 20 and FIG. 21. In FIG. 20 and FIG.21, as an example, a manufacturing process for the solid-state imagingdevice 4 is shown.

As shown in (1) in FIG. 20, the light-receiving sections 12 thatphotoelectrically convert incident light, the pixel separation areas 13that separate the light-receiving sections 12, the peripheral circuitsection 14 in which peripheral circuits (e.g., a circuit 14C) are formedwith respect to the light-receiving section 12 via the pixel separationarea 13, and the like are formed in the semiconductor substrate (or thesemiconductor layer) 11. An existing manufacturing method is used forthe manufacturing method.

The film 21 for reducing interface state density that has permeabilityto the incident light is formed. The film 21 for reducing interfacestate density is formed by, for example, a silicon oxide film.

Moreover, the film 25 for separating a film having negative fixedcharges from a light-receiving surface is formed on the film 21 forreducing interface state density. The film 25 desirably has positivefixed charges to cancel the influence of the negative fixed charges.Silicon nitride is preferably used for the film 25. The film 25 ishereinafter referred to as film having positive fixed charges.

At least on the light-receiving sections 12, the film 21 for reducinginterface state density needs to be formed, by the film 22 havingnegative fixed charges formed later, in thickness enough for forming thehole accumulation layers 23, described later, on the light-receivingsurfaces 12 s side of the light-receiving sections 12. The filmthickness is, for example, equal to or larger than one atom layer andequal to or smaller than 100 nm.

As shown in (2) in FIG. 20, a resist mask 52 is formed on the film 25having positive fixed charges above the peripheral circuit section 14 bythe resist application and the lithography technique.

As shown in (3) in FIG. 21, the film 25 having positive fixed charges isetched by using the resist mask 52 (see (2) in FIG. 20) to leave thefilm 25 having positive fixed charges on the peripheral circuit section14. Thereafter, the resist mask 52 is removed.

As shown in (4) in FIG. 21, the film 22 having negative fixed chargesthat covers the film 25 having positive fixed charges is formed on thefilm 21 for reducing interface state density.

The film 22 having negative fixed charges is formed by, for example, ahafnium oxide (HfO₂) film, an aluminum oxide (Al₂O₃) film, a zirconiumoxide (ZrO₂) film, a tantalum oxide (Ta₂O₅) film, or a titanium oxide(TiO₂) film. The films of the kinds described above are actually used ina gate insulating film and the like of an insulated-gate field-effecttransistor. Therefore, since a film forming method is established, it ispossible to easily form the films. As the film forming method, forexample, the chemical vapor deposition method, the sputtering method,and the atomic layer deposition method can be used. The atomic layerdeposition method is suitably used because an SiO₂ layer for reducinginterface state density can be simultaneously formed by about 1 nmduring the film formation.

As materials other than the above, lanthanum oxide (La₂O₃), praseodymiumoxide (Pr₂O₃), cerium oxide (CeO₂), neodymium oxide (Nd₂O₃), promethiumoxide (Pm₂O₃), samarium oxide (Sm₂O₃), europium oxide (Eu₂O₃),gadolinium oxide (Gd₂O₃), terbium oxide (Tb₂O₃), dysprosium oxide(Dy₂O₃), holmium oxide (Ho₂O₃), erbium oxide (Er₂O₃), thulium oxide(Tm₂O₃), ytterbium oxide (Yb₂O₃), lutetium oxide (Lu₂O₃), yttrium oxide(Y₂O₃), and the like can be used. The film 22 having negative fixedcharges can be formed by a hafnium nitride film, an aluminum nitridefilm, a hafnium oxide nitride film, or an aluminum oxide nitride film aswell. These films can also be formed by, for example, the chemical vapordeposition method, the sputtering method, and the atomic layerdeposition method.

Silicon (Si) or nitrogen (N) may be added to the film 22 having negativefixed charges as long as insulating properties thereof are not spoiled.The density of silicon or nitrogen is appropriately determined in arange in which the insulating properties of the film are not spoiled.Such addition of silicon (Si) or nitrogen (N) makes it possible toimprove heat resistance of the film and an ability of blocking ionimplantation in a process.

When the film 22 having negative fixed charges is formed by a hafniumoxide (HfO₂) film, it is possible to efficiently obtain a reflectionprevention effect by adjusting the film thickness of the hafnium oxide(HfO₂) film. Naturally, when other kinds of films are used, it ispossible to obtain the reflection prevention effect by optimizing filmthickness according to a refractive index.

In the configuration on the film 22 having negative fixed charges in thesolid-state imaging device 5, a light shielding film that shields a partof the light-receiving sections 12 and the peripheral circuit section14, a color filter layer that splits light made incident on at least thelight-receiving sections 12, a condensing lens that condenses theincident light on the light-receiving sections 12, and the like areprovided. As an example, as the configuration, the configuration of anyone of the solid-state imaging devices 1, 2, and 3 can also be applied.

In the manufacturing method (the first manufacturing method) for asolid-state imaging device according to the fifth embodiment, the film22 having negative fixed charges is formed on the film 21 for reducinginterface state density. Therefore, the hole accumulation layer 23 issufficiently formed in the interface on the light-receiving surfacesside of the light-receiving sections 12 by an electric field due to thenegative fixed charges in the film 22 having negative fixed charges.

Therefore, charges (electrons) generated from the interface can besuppressed. Even if charges (electrons) are generated from the electricfield, since the charges (electrons) flow in the hole accumulationlayers 23 in which a large number of holes are present without flowinginto charge accumulation portions forming wells of potential in thelight-receiving sections 12, the charges (the electrons) can beeliminated.

Therefore, it is possible to prevent dark currents generated by thecharges due to the interface from being detected by the light-receivingsections and suppress the dark currents due to the interface statedensity.

Further, since the film 21 for reducing interface state density isformed on the light-receiving surfaces of the light-receiving sections12, the generation of electrons due to the interface state density isfurther suppressed. Therefore, the electrons due to the interface statedensity are prevented from flowing into the light-receiving sections 12as dark currents.

Since the film 22 having negative fixed charges is used, it is possibleto form an HAD structure without applying ion implantation and annealingthereto.

Moreover, the film 25 preferably having positive fixed charges and usedfor separating a film having negative fixed charges from the surface ofa light-receiving surface is formed between the peripheral circuitsection 14 and the film 22 having negative fixed charges. Therefore, thenegative fixed charges of the film 22 having negative fixed charges arereduced by the positive fixed charges in the film 25 having positivefixed charges. This prevents the electric field of the negative fixedcharges in the film 22 having negative fixed charges from affecting theperipheral circuit section 14.

Therefore, it is possible to prevent a malfunction of the peripheralcircuit section 14 due to the negative fixed charges.

Presence of negative fixed charges in a hafnium oxide (HfO₂) film as anexample of the film having negative fixed charges is explained below.

As a first sample, a MOS capacitor in which agate electrode was formedon a silicon substrate via a thermal silicon oxide (SiO₂) film and thethickness of the thermal silicon oxide film was changed was prepared.

As a second sample, a MOS capacitor in which a gate electrode was formedon a silicon substrate via a CVD silicon oxide (CVD-SiO₂) film and thethickness of the CVD silicon oxide film was changed was prepared.

As a third sample, a MOS capacitor in which a gate electrode was formedon a silicon substrate via a laminated film obtained by laminating anozone silicon oxide (O₃—SiO₂) film, a hafnium oxide (HfO₂) film, and aCVD silicon oxide (SiO₂) film in order and the thickness of the CVDsilicon oxide film was changed was prepared. The thickness of the HfO₂film and the thickness of the O₃—SiO₂ film were fixed.

The CVD-SiO₂ films of the respective samples are formed by the CVDmethod using a mixed gas of monosilane (SiH₄) and oxygen (O₂). The HfO₂film is formed by the ALD method using tetrakisethylmethyl-amino hafnium(TEMAHf) and ozone (O₃) as materials. The O₃—SiO₂ film in the thirdsample is an interface oxide film having the thickness of about 1 nmformed between HfO₂ and a silicon substrate when the HfO₂ film is formedby the ALD method. In all the gate electrodes in the samples, thestructure in which an aluminum (Al) film, a titanium nitride (TiN) film,and a titanium (Ti) film are laminated from above is used.

In the sample structure, in the first sample and the second sample, thegate electrode was formed right above the SiO₂ film. On the other hand,in only an applied product of the HfO₂ film of the third sample, theCVD-SiO₂ film was laminated on the HfO₂ film. This is for the purpose ofpreventing, by directly setting HfO₂ and the gate electrode in contactwith each other, HfO₂ and the electrode from causing a reaction in aninterface thereof.

In the laminated structure of the third sample, the HfO₂ film thicknesswas fixed to 10 nm and the thickness of the CVD-SiO₂ film above waschanged. This is because, since HfO₂ has a large relative dielectricconstant and the thickness in terms of an oxide film is severalnanometers even when film thickness is at the level of 10 nm, it isdifficult to see a change in a flat band voltage Vfb with respect to theeffective thickness of the silicon oxide layer (oxide film equivalentthickness).

The flat band voltage Vfb with respect to oxide film equivalentthickness Tox was checked for the first sample, the second sample, andthe third sample. A result of the check is shown in FIG. 22.

As shown in FIG. 22, in the first sample of the thermal oxide(Thermal-SiO₂) film and the second sample of the CVD-SiO₂ film, the flatband voltage shifts in a minus direction with respect to an increase inthe film thickness.

On the other hand, only in the applied product of the HfO₂ film of thethird sample, it could be confirmed that the flat band voltage shiftedin a plus direction with respect to an increase in the film thickness.According to the behavior of the flat band voltage, it is seen thatminus charges are present in the HfO₂ film.

Concerning materials forming the film having negative fixed chargesother than HfO₂, it is known that the materials have negative fixedcharges in the same manner as HfO₂.

Data of interface state density in the respective samples is shown inFIG. 23. In FIG. 23, interface state density Dit is compared by usingthe first, second, and third samples, oxide film equivalent thicknessesTox of which are substantially equal at about 40 nm in FIG. 22.

As a result, as shown in FIG. 23, whereas the first sample of thethermal oxide (Thermal-SiO₂) film has a characteristic equal to or lowerthan 2E10 (cm²·eV), the interface state density is deteriorated by onedigit in the second sample of the CVD-SiO₂ film.

On the other hand, it can be confirmed that the third sample in whichthe HfO₂ film is used has a satisfactory interface close to that of thethermal oxide film at about 3E10/cm²·eV.

Concerning the materials forming the film having negative fixed chargesother than HfO₂, it is known that, like HfO₂, the materials have thesatisfactory interface state density close to that of the thermal oxidefilm.

When the film 25 having positive fixed charges was formed, the flat bandvoltage Vfb with respect to the oxide film equivalent thickness Tox waschecked. A result of the check is shown in FIG. 24.

As shown in FIG. 24, when the flat band voltage Vfb is larger than theflat band voltage of the thermal oxide film, negative charges arepresent in a film. Holes are formed in the silicon (Si) surface. As sucha laminated film, for example, there is a laminated film in which anHfO₂ film and a CVD-SiO₂ film are laminated in order from below on thesurface of a silicon (Si) substrate.

On the other hand, when the flat band voltage Vfb is smaller than theflat band voltage of the thermal oxide film, positive charges arepresent in a film. Electrons are formed in the silicon (Si) surface. Assuch a laminated film, for example, there is a laminated film in which aCVD-SiO₂ film, a CVD-SiN film, an HfO₂ film, and a CVD-SiO₂ film arelaminated in order from below on the surface of a silicon (Si)substrate. When the thickness of the CVD-SiN film is increased, the flatband voltage substantially shifts in a minus direction compared with thethermal oxide film. The influence of positive charges in the CVD-SiNfilm cancels negative charges in hafnium oxide (HfO₂).

In the solid-state imaging device 1 to the solid-state imaging device 5according to the embodiments, as explained above, when nitrogen (N) iscontained in the film 22 having negative fixed charges, after formingthe film 22 having negative fixed charges, it is possible to containnitrogen (N) in the film 22 with nitriding by high-frequency plasma ormicrowave plasma.

It is possible to increase the negative fixed charges in the film 22having negative fixed charges by applying electron beam curing byelectron beam irradiation to the film 22 having negative fixed chargesafter forming the film.

A preferred manufacturing method according to a sixth embodiment in thecase in which hafnium oxide is used for the film 22 having negativefixed charges used in the manufacturing methods (the first manufacturingmethods) for a solid-state imaging device according to the first tofifth embodiments is explained below with reference to FIG. 25. In FIG.25, as an example, the manufacturing method is applied to the firstmanufacturing method according to the first embodiment. A method offorming a film having negative fixed charges according to thisembodiment can be applied to methods of forming a film having negativefixed charges of the first manufacturing methods according to the secondto fifth embodiments as well.

When the film 22 having negative fixed charges is formed of oxidehafnium by the atomic layer deposition method (the ALD method), althougha film quality is excellent, film formation time is long.

Therefore, as shown in (1) in FIG. 25, the semiconductor substrate (orthe semiconductor layer) 11 on which the light-receiving section 12 thatphotoelectrically converts incident light, the pixel separation areas 13that separate the light-receiving section 12, the peripheral circuitsection 14 in which peripheral circuits (not specifically shown) areformed with respect to the light-receiving section 12 via the pixelseparation area 13, and the like are formed is prepared. The film 21 forreducing interface state density is formed on the light-receivingsurface 12 s of the light-receiving section 12, actually, on thesemiconductor substrate 11.

A first hafnium oxide film 22-1 is formed on the film 21 for reducinginterface state density by the atomic layer deposition method. The firsthafnium oxide film 22-1 is formed in thickness at least equal to orlarger than 3 nm of thickness necessary for the film 22 having negativefixed charges.

As an example of a film formation condition of the atomic layerdeposition method (the ALD method) for forming the first hafnium oxidefilm 22-1, TEMA-Hf (Tetrakis ethylmethylamido hafnium), TDMA-Hf(Tetrakis dimethylamido hafnium), or TDEA-Hf (Tetrakis diethylamidohafnium) was used as a precursor, film formation substrate temperaturewas set to 200° C. to 500° C., a flow rate of the precursor was set to10 cm³/min to 500 cm³/min, irradiation time of the precursor was set to1 second to 15 seconds, and a flow rate of ozone (O₃) was set to 5cm³/min to 50 cm³/min.

The first hafnium oxide film 22-1 can be formed by the organic metalchemical vapor deposition method (the MOCVD method) as well. As anexample of a film formation condition in this case, EMA-Hf (Tetrakisethylmethylamino hafnium), TDMA-Hf (Tetrakis dimethylamino hafnium), orTDEA-Hf (Tetrakis diethylamnio hafnium) was used as a precursor, filmformation substrate temperature was set to 200° C. to 600° C., a flowrate of the precursor was set to 10 cm³/min to 500 cm³/min, irradiationtime of the precursor was set to 1 second to 15 seconds, and a flow rateof ozone (O₃) was set to 5 cm³/min to 50 cm³/min.

As shown in (2) in FIG. 25, a second hafnium oxide film 22-2 is formedon the first hafnium oxide film 22-1 by the physical vapor depositionmethod (the PVD method) to complete the film 22 having negative fixedcharges. For example, the second hafnium oxide film 22-2 is formed suchthat the total thickness of the first hafnium oxide film 22-1 and thesecond hafnium oxide film 22-2 is 50 nm to 60 nm.

Thereafter, as explained in the first to fifth embodiments, thefollowing process for forming the insulating film 41 on the film 22having negative fixed charges is performed.

As an example of a film formation condition in the physical vapordeposition method (the PVD method) of the second hafnium oxide film22-2, a hafnium metal target was used as a target, argon and oxygen wereused as process gasses, the voltage of a film formation atmosphere wasset to 0.01 Pa to 50 Pa, power was set to 500 W to 2.00 kW, a flow rateof argon (Ar) was set to 5 cm³/min to 50 cm³/min, and a flow rate ofoxygen (O₂) was set to 5 cm³/min to 50 cm³/min.

The thickness of the film 22 having negative fixed charges formed ofhafnium oxide was set to 60 nm. A C-V (capacity-voltage) characteristicof the solid-state imaging device in this case was checked using thethickness of the first hafnium oxide film 22-1 as a parameter.

A result of the check is shown in FIGS. 26 and 27. In both FIGS. 26 and27, the ordinate indicates capacity (C) and the abscissa indicatesvoltage (V).

As shown in FIG. 26, when a hafnium oxide (HfO₂) film is formed by onlythe PVD method, the flat band voltage Vfb is −1.32 V, which is negativevoltage. The film is not a film having negative fixed charges.

The flat band voltage Vfb needs to be positive voltage to obtain a filmhaving negative fixed charges.

Since a rising edge is dull, interface state density is large. Asexplained later, in this case, the evaluation of the interface statedensity Dit was unavailable because the interface state density is toohigh.

On the other hand, when, after the first hafnium oxide film 22-1 isformed in the thickness of 3 nm by the ALD method, the second hafniumoxide film 22-2 is formed in the thickness of 50 nm on the first hafniumoxide film 22-1 by the PVD method, the flat band voltage Vfb is +0.42V,which is positive voltage. Therefore, the film is a film having negativefixed charges.

Since a rising edge is steep, the interface state density Dit is low at5.14E10/cm²·eV.

When, after the first hafnium oxide film 22-1 is formed in the thicknessof 11 nm by the ALD method, the second hafnium oxide film 22-2 is formedin the thickness of 50 nm on the first hafnium oxide film 22-1 by thePVD method, the flat band voltage Vfb is higher positive voltage.Therefore, the film is a film having negative fixed charges.

Since a rising edge is steeper, the interface state density Dit islower.

As shown in FIG. 27, when, after the first hafnium oxide film 22-1 isformed in the thickness of 11 nm by the ALD method, the second hafniumoxide film 22-2 is formed in the thickness of 50 nm on the first hafniumoxide film 22-1 by the PVD method, the flat band voltage Vfb close tothat obtained when the film 22 having negative fixed charges is entirelyformed by the ALD method is obtained. A rising edge is in a statesubstantially close to that obtained when the film 22 having negativefixed charges is entirely formed by the ALD method.

A film having negative fixed charges was obtained when, after the firsthafnium oxide film 22-1 was formed in the thickness of 11 nm, the secondhafnium oxide film 22-2 was formed in the thickness of 50 nm on thefirst hafnium oxide film 22-1 by the PVD method. Concerning this film,general measurement of a C-V characteristic (Qs-CV: Quasi-static-CV)with a direct current and measurement (Hf—CV) with a high-frequency wavewere performed. The Qs-CV measurement is a measurement method forsweeping gate voltage as a linear function of time and calculating adisplacement current flowing between a gate and a substrate. Capacitancein a low-frequency region is calculated from the displacement current.

A result of the measurement is shown in FIG. 28.

The interface state density Dit was calculated from a difference betweena measurement value of Qs-CV and a measurement value of Hf—CV. As aresult, Dit was 5.14E10/cm²·eV, which was a sufficiently low value. Asexplained above, the flat band voltage Vfb was +0.42 V, which waspositive voltage.

Therefore, it is possible to set a value of the flat band voltage Vfb ofthe film 22 having negative fixed charges to a positive voltage and setthe interface state density Dit low by forming the first hafnium oxidefilm 22-1 in the thickness equal to or larger than 3 nm.

It is preferable to form the first hafnium oxide film 22-1 in thicknessequal to or larger than 3 nm of thickness necessary for the film 22having negative fixed charges.

The first hafnium oxide film 22-1 is a film formed by the atomic layerdeposition method. In the formation of a hafnium oxide film by theatomic layer deposition method, at the film thickness thereof smallerthan 3 nm, when the next formation of the second hafnium oxide film 22-2is performed by the PVD method, interface damage due to the PVD methodoccurs. However, when the thickness of the first hafnium oxide film 22-1is increased to be equal to or larger than 3 nm, the interface damage issuppressed even when the next formation of the second hafnium oxide film22-2 is performed by the PVD method. When the thickness of the firsthafnium oxide film 22-1 is set to be equal to or larger than 3 nm tosuppress the interface damage due to the PVD method in this way, in afilm obtained by combining the first hafnium oxide film 22-1 and thesecond hafnium oxide film 22-2, a value of the flat band voltage Vfb ispositive voltage. Therefore, the film is a film having negative fixedcharges.

Therefore, the first hafnium oxide film 22-1 formed on the side of theinterface with the film 21 for reducing interface state density has thethickness equal to or smaller than 3 nm.

As an example of the PVD method, there is the sputtering method.

On the other hand, when the film 22 having negative fixed charges isentirely formed by the atomic layer deposit method, although the C-Vcharacteristic is excellent, since film formation takes too long time,productivity markedly falls. Therefore, it is difficult to set thethickness of the first hafnium oxide film 22-1 very large.

In the atomic layer deposit method, for example, it takes aboutforty-five minutes to form a hafnium oxide film in the thickness of 10nm. On the other hand, in the physical vapor deposition method, forexample, it takes only about three minutes to form a hafnium oxide filmin the thickness of 50 nm. Therefore, an upper limit of the thickness ofthe first hafnium oxide film 22-1 is determined by taking into accountproductivity. For example, when formation time for the film 22 havingnegative fixed charges is within one hour, an upper limit of thethickness of the first hafnium oxide film 22-1 is about 11 nm to 12 nm.

With the film formation method employing both the atomic layerdeposition method and the physical vapor deposition method, it ispossible to substantially reduce film formation time from time forforming the film 22 having negative fixed charges entirely with theatomic layer deposition method or the CVD method. Therefore, it ispossible to realize improvement of mass production efficiency.

In the atomic layer deposition method and the MOCVD method, there isalmost no damage to a substrate compared with the film formation by thephysical vapor deposition method.

Therefore, damage to a light-reception sensor unit is reduced. Theproblem of increasing interface state density as a cause of generationof dark currents can be solved.

In the above explanation, the film 22 having negative fixed charges isformed by a hafnium oxide film. However, the manufacturing methodaccording to this embodiment for, first, forming a film with the atomiclayer deposition method and, then, forming a film with the physicalvapor deposition method can be applied in the same manner to the film 22having negative fixed charges formed by the films explained above.Examples of the films include the aluminum oxide (Al₂O₃) film, thezirconium oxide (ZrO₂) film, the tantalum oxide (Ta₂O₅) film, and the atitanium oxide (TiO₂) film, the films of lanthanum oxide (La₂O₃),praseodymium oxide (Pr₂O₃), cerium oxide (CeO₂), neodymium oxide(Nd₂O₃), promethium oxide (Pm₂O₃), samarium oxide (Sm₂O₃), europiumoxide (Eu₂O₃), gadolinium oxide (Gd₂O₃), terbium oxide (Tb₂O₃),dysprosium oxide (Dy₂O₃), holmium oxide (Ho₂O₃), erbium oxide (Er₂O₃),thulium oxide (Tm₂O₃), ytterbium oxide (Yb₂O₃), lutetium oxide (Lu₂O₃),yttrium oxide (Y₂O₃), and the like, and the hafnium nitride film, thealuminum nitride film, the hafnium oxide nitride film, and the aluminumoxide nitride film. In this case, effects same as those in the case ofthe hafnium oxide film can be obtained.

A preferred manufacturing method according to a seventh embodiment forthe film 22 having negative fixed charges used in the manufacturingmethods (the first manufacturing methods) for a solid-state imagingdevice according to the first to fifth embodiments is explained belowwith reference to FIG. 29 to FIG. 31. In FIG. 29 to FIG. 31, as anexample, the manufacturing method is applied the first manufacturingmethod according to the first embodiment. A method of forming a filmhaving negative fixed charges according to this embodiment can beapplied to the methods of forming a film having negative fixed chargesof the first manufacturing methods according to the second to fifthembodiments as well. In this explanation, as an example of a film havingnegative fixed charges, a hafnium oxide film is used.

As shown in (1) in FIG. 29, the plural light-receiving sections 12 thatphotoelectrically convert incident light, the peripheral circuit section14 in which peripheral circuits (not specifically shown) for processingsignals photoelectrically converted and obtained by the respectivelight-receiving sections 12 are formed, the pixel separation areas 13that separate, for example, the light-receiving section 12 and theperipheral circuit section 14, the light-receiving sections 12 (thepixel separation areas 13 among the light-receiving sections 12 are notshown), and the like are formed in the semiconductor substrate (or thesemiconductor layer) 11. An existing manufacturing method is used forthe manufacturing method.

As shown in (2) in FIG. 29, the film 21 for reducing interface statedensity is formed on the light-receiving surfaces 12 s of thelight-receiving sections 12, actually, on the semiconductor substrate11. The film 21 for reducing interface state density is formed by, forexample, a silicon oxide (SiO₂) film.

The film 22 having negative fixed charges is formed on the film 21 forreducing interface state density. Consequently, the hole accumulationlayers 23 are formed on the light-receiving surfaces side of thelight-receiving sections 12.

Therefore, at least on the light-receiving sections 12, the film 21 forreducing interface state density needs to be formed, by the film 22having negative fixed charges, in thickness enough for forming the holeaccumulation layers 23 on the light-receiving surfaces 12 s side of thelight-receiving sections 12. The film thickness is, for example, equalto or larger than one atom layer and equal to or smaller than 100 nm.

The film 22 having negative fixed charges is formed by, for example, ahafnium oxide (HfO₂) film, an aluminum oxide (Al₂O₃) film, a zirconiumoxide (ZrO₂) film, a tantalum oxide (Ta₂O₅) film, or a titanium oxide(TiO₂) film. The films of the kinds described above are actually used ina gate insulating film and the like of an insulated-gate field-effecttransistor. Therefore, since a film forming method is established, it ispossible to easily form the films. As the film forming method, forexample, the chemical vapor deposition method, the sputtering method,and the atomic layer deposition method can be used. The atomic layerdeposition method is suitably used because an SiO₂ layer for reducinginterface state density can be simultaneously formed by about 1 nmduring the film formation.

As materials other than the above, lanthanum oxide (La₂O₃), praseodymiumoxide (Pr₂O₃), cerium oxide (CeO₂), neodymium oxide (Nd₂O₃), promethiumoxide (Pm₂O₃), samarium oxide (Sm₂O₃), europium oxide (Eu₂O₃),gadolinium oxide (Gd₂O₃), terbium oxide (Tb₂O₃), dysprosium oxide(Dy₂O₃), holmium oxide (Ho₂O₃), erbium oxide (Er₂O₃), thulium oxide(Tm₂O₃), ytterbium oxide (Yb₂O₃), lutetium oxide (Lu₂O₃), yttrium oxide(Y₂O₃), and the like can be used. For these films, for example, thechemical vapor deposition method, the sputtering method, and the atomiclayer deposition method can be used.

When the film 22 having negative fixed charges is formed by a hafniumoxide (HfO₂) film, it is possible to efficiently obtain a reflectionprevention effect by adjusting the thickness of the hafnium oxide (HfO₂)film. Naturally, when other kinds of films are used, it is possible toobtain the reflection prevention effect by optimizing film thicknessaccording to a refractive index.

The surface of the film 22 having negative fixed charges is subjected toplasma nitriding.

Negative fixed charges are further generated in the hafnium oxide filmaccording to the plasma nitriding and larger band bending is formed. Asa plasma nitriding condition, for example, a high-frequency plasmaprocessing device is used and nitrogen (N₂) or ammonium (NH₃) is used asgas for nitriding supplied into a chamber and, for example, RF power isset to 200 W to 900 W and voltage is set to 0.13 Pa to 13.3 Pa. Underthis condition, plasma is generated in the chamber to perform nitriding.

A plasma processing device is not limited to the high-frequency plasmaprocessing device. Any plasma processing device may be used as long asplasma can be generated in the chamber. For example, a microwave plasmaprocessing device, an ICP plasma processing device, an ECR plasmaprocessing device, and the like can be used.

The plasma nitriding is performed such that nitrogen (N) is introducedinto the surface of the film 22 having negative fixed charges. It isimportant to set a plasma nitriding condition to perform the plasmanitriding such that nitrogen (N) does not reach an interface on thelight-receiving sections 12 side of the film 22 having negative fixedcharges. For example, supply amounts of nitrogen gas and ammonium gas tothe chamber, RF power, and the like only have to be adjusted by takinginto account the thickness, a material, and the like of the film 22having negative fixed charges.

When nitrogen (N) reaches the interface on the light-receiving sections12 side of the film 22 having negative fixed charges, nitrogen causesoccurrence of a white dot defect in the light-receiving sections 12.

As shown in (3) in FIG. 30, the insulating film 41 is formed on the film22 having negative fixed charges. The light shielding film 42 is formedon the insulating film 41. The insulating film 41 is formed by, forexample, a silicon oxide film. The light shielding film 42 is formed by,for example, a metal film having light shielding properties.

The light shielding film 42 is formed on the film 22 having negativefixed charges via the insulating film 41 in this way. This makes itpossible to prevent a reaction of the film 22 having negative fixedcharges formed by a hafnium oxide film or the like and the metal of thelight shielding film 42.

When the light shielding film 42 is etched, since the insulating film 41functions as an etching stopper, it is possible to prevent etchingdamage to the film 22 having negative fixed charges.

As shown in (4) in FIG. 30, a resist mask (not shown) is formed on thelight shielding film 42 above a part of the light-receiving sections 12and the peripheral circuit section 14 by the resist application and thelithography technique. The light shielding film 42 is etched by usingthe resist mask to leave the light shielding film 42 on the insulatingfilm 41 above a part of the light-receiving sections 12 and theperipheral circuit section 14.

An area in which light does not enter is formed in the light-receivingsections 12 by the light shielding film 42. A black level in an image isdetermined by an output of the light-receiving sections 12.

Since light is prevented from entering the peripheral circuit section14, fluctuation in characteristics caused by the light entering theperipheral circuit section 14 is suppressed.

As shown in (5) in FIG. 31, the insulating film 43 that reduces a stepformed by the light shielding film 42 is formed on the insulating film41. The insulating film 43 is preferably planarized on the surfacethereof and is formed by, for example, a coated insulating film.

As shown in (6) in FIG. 31, the color filter layer 44 is formed on theinsulating film 43 above the light-receiving section 12 by an existingmanufacturing technique. The condensing lens 45 is formed on the colorfiler layer 44. A light transmissive insulating film (not shown) may beformed between the color filter layer 44 and the condensing lens 45 inorder to prevent machining damage to the color filter layer 44 in lensmachining.

The solid-state imaging device 1 is formed in this way.

A state of generation of dark currents according to presence or absenceof the plasma nitriding in the solid-state imaging device 1 in which ahafnium oxide (HfO₂) film was used for the film 22 having negative fixedcharges was checked. A result of the check is shown in FIG. 32.

In FIG. 32, the ordinate indicates a percentage of generation (%) ofdark currents and the abscissa indicates dark currents normalized by amedian of dark currents in only the hafnium oxide film (HfO₂).

As shown in FIG. 32, it is seen that, in a solid-state imaging device inwhich a film having negative fixed charges obtained by subjecting thesurface of a hafnium oxide film to plasma nitriding is used, darkcurrents are substantially reduced from those in a solid-state imagingdevice in which a hafnium nitride film not subjected to plasma nitridingis used for a film having negative fixed charges.

In the film 22 having negative fixed charges including the various filmsother than the hafnium oxide film, as in the hafnium oxide film, it ispossible to obtain an effect that the solid-state imaging device inwhich a film having negative fixed charges obtained by subjecting thesurface of a hafnium oxide film to plasma nitriding is used cansubstantially reduce dark currents compared with the solid-state imagingdevice in which a hafnium nitride film not subjected to plasma nitridingis used for a film having negative fixed charges.

Therefore, in the manufacturing method (the first manufacturing method)for a solid-state imaging device according to the seventh embodiment,since the surface of the film 22 having negative fixed charges issubjected to plasma nitriding, the negative fixed charges in the film 22having negative fixed charges increase and stronger band bending can beformed. Therefore, dark currents generated in the light-receivingsection 12 can be reduced.

A preferred manufacturing method according to an eighth embodiment forthe film 22 having negative fixed charges used in the manufacturingmethods (the first manufacturing methods) for a solid-state imagingdevice according to the first to fifth embodiments is explained belowwith reference to FIG. 33 to FIG. 35. In FIG. 33 to FIG. 35, as anexample, the manufacturing method is applied the first manufacturingmethod according to the first embodiment. A method of forming a filmhaving negative fixed charges according to this embodiment can beapplied to the methods of forming a film having negative fixed chargesof the first manufacturing methods according to the second to fifthembodiments as well. In this explanation, as an example of a film havingnegative fixed charges, a hafnium oxide film is used.

As shown in (1) in FIG. 33, the plural light-receiving sections 12 thatphotoelectrically convert incident light, the peripheral circuit section14 in which peripheral circuits (not specifically shown) for processingsignals photoelectrically converted and obtained by the respectivelight-receiving sections 12 are formed, the pixel separation areas 13that separate the light-receiving sections 12 and the peripheral circuitsection 14, the light-receiving sections 12 (the pixel separation areas13 among the light-receiving sections 12 are not shown), and the likeare formed in the semiconductor substrate (or the semiconductor layer)11. An existing manufacturing method is used for the manufacturingmethod.

As shown in (2) in FIG. 33, the film 21 for reducing interface statedensity is formed on the light-receiving surfaces 12 s of thelight-receiving sections 12, actually, on the semiconductor substrate11. The film 21 for reducing interface state density is formed by, forexample, a silicon oxide (SiO₂) film.

The film 22 having negative fixed charges is formed on the film 21 forreducing interface state density. Consequently, the hole accumulationlayer 23 is formed on the light-receiving surface sides of thelight-receiving sections 12.

Therefore, at least on the light-receiving section 12, the film 21 forreducing interface state density needs to be formed, by the film 22having negative fixed charges, in thickness enough for forming the holeaccumulation layer 23 on the light-receiving surface 12 s side of thelight-receiving section 12. The film thickness is, for example, equal toor larger than one atom layer and equal to or smaller than 100 nm.

The film 22 having negative fixed charges is formed by, for example, ahafnium oxide (HfO₂) film, an aluminum oxide (Al₂O₃) film, a zirconiumoxide (ZrO₂) film, a tantalum oxide (Ta₂O₅) film, or a titanium oxide(TiO₂) film. The films of the kinds described above are actually used ina gate insulating film and the like of an insulated-gate field-effecttransistor. Therefore, since a film forming method is established, it ispossible to easily form the films. As the film forming method, forexample, the chemical vapor deposition method, the sputtering method,and the atomic layer deposition method can be used. The atomic layerdeposition method is suitably used because an SiO₂ layer for reducinginterface state density can be simultaneously formed by about 1 nmduring the film formation.

As materials other than the above, lanthanum oxide (La₂O₃), praseodymiumoxide (Pr₂O₃), cerium oxide (CeO₂), neodymium oxide (Nd₂O₃), promethiumoxide (Pm₂O₃), samarium oxide (Sm₂O₃), europium oxide (Eu₂O₃),gadolinium oxide (Gd₂O₃), terbium oxide (Tb₂O₃), dysprosium oxide(Dy₂O₃), holmium oxide (Ho₂O₃), erbium oxide (Er₂O₃), thulium oxide(Tm₂O₃), ytterbium oxide (Yb₂O₃), lutetium oxide (Lu₂O₃), yttrium oxide(Y₂O₃), and the like can be used. For these films, for example, thechemical vapor deposition method, the sputtering method, and the atomiclayer deposition method can be used.

When the film 22 having negative fixed charges is formed by a hafniumoxide (HfO₂) film, it is possible to efficiently obtain a reflectionprevention effect by adjusting the film thickness of the hafnium oxide(HfO₂). Naturally, when other kinds of films are used, it is possible toobtain the reflection prevention effect by optimizing film thicknessaccording to a refractive index.

The surface of the film 22 having negative fixed charges is subjected toplasma nitriding.

Negative fixed charges are further generated in the hafnium oxide filmaccording to the plasma nitriding and larger band bending is formed. Asa plasma nitriding condition, for example, an electron beam irradiatingdevice is used, for example, acceleration voltage is set to 0.5 kV to 50kV, voltage in a chamber is set to 0.13 Pa to 13.3 Pa, and substratetemperature is set to 200° C. to 500° C. An electron beam is irradiatedon the surface of the film 22 to perform electron beam curing.

As shown in (3) in FIG. 34, the insulating film 41 is formed on the film22 having negative fixed charges. The light shielding film 42 is formedon the insulating film 41. The insulating film 41 is formed by, forexample, a silicon oxide film. The light shielding film 42 is formed by,for example, a metal film having light shielding properties.

The light shielding film 42 is formed on the film 22 having negativefixed charges via the insulating film 41 in this way. This makes itpossible to prevent a reaction of the film 22 that is formed by ahafnium oxide film or the like and has having negative fixed charges andthe metal of the light shielding film 42.

When the light shielding film 42 is etched, since the insulating film 41functions as an etching stopper, it is possible to prevent etchingdamage to the film 22 having negative fixed charges.

As shown in (4) in FIG. 34, a resist mask (not shown) is formed on thelight shielding film 42 above a part of the light-receiving sections 12and the peripheral circuit section 14 by the resist application and thelithography technique. The light shielding film 42 is etched by usingthe resist mask to leave the light shielding film 42 on the insulatingfilm 41 above a part of the light-receiving sections 12 and theperipheral circuit section 14.

An area in which light does not enter is formed in the light-receivingsections 12 by the light shielding film 42. A black level in an image isdetermined by an output of the light-receiving sections 12.

Since light is prevented from entering the peripheral circuit section14, fluctuation in characteristics caused by the light entering theperipheral circuit section 14 is suppressed.

As shown in (5) in FIG. 35, the insulating film 43 that reduces a stepformed by the light shielding film 42 is formed on the insulating film41. The insulating film 43 is preferably planarized on the surfacethereof and is formed by, for example, a coated insulating film.

As shown in (6) in FIG. 35, the color filter layer 44 is formed on theinsulating film 43 above the light-receiving sections 12 by an existingmanufacturing technique. The condensing lens 45 is formed on the colorfiler layer 44. A light transmissive insulating film (not shown) may beformed between the color filter layer 44 and the condensing lens 45 inorder to prevent machining damage to the color filter layer 44 in lensmachining.

The solid-state imaging device 1 is formed in this way.

A state of generation of dark currents according to presence or absenceof the electron beam curing in the solid-state imaging device 1 in whicha hafnium oxide (HfO₂) film was used for the film 22 having negativefixed charges was checked. A result of the check is shown in FIG. 36.

In FIG. 36, the ordinate indicates a percentage of generation (%) ofdark currents and the abscissa indicates dark currents normalized by amedian of dark currents of only the hafnium oxide film (HfO₂).

As shown in FIG. 36, it is seen that, in a solid-state imaging device inwhich a film having negative fixed charges obtained by subjecting thesurface of a hafnium oxide film to electron beam curing is used, darkcurrents can be substantially reduced from those in a solid-stateimaging device in which a hafnium nitride film not subjected to electronbeam curing is used for a film having negative fixed charges.

In the film 22 having negative fixed charges including the various filmsother than the hafnium oxide film, as in the hafnium oxide film, it ispossible to obtain an effect that the solid-state imaging device inwhich a film having negative fixed charges obtained by subjecting thesurface of a hafnium oxide film to electron beam curing is used cansubstantially reduce dark currents compared with the solid-state imagingdevice in which a hafnium nitride film not subjected to electron beamcuring is used for a film having negative fixed charges.

Therefore, in the manufacturing method (the first manufacturing method)for a solid-state imaging device according to the eighth embodiment,since the surface of the film 22 having negative fixed charges issubjected to electron beam curing, the negative fixed charges in thefilm 22 having negative fixed charges increase and stronger band bendingcan be formed. Therefore, dark currents generated in the light-receivingsection 12 can be reduced.

A preferred manufacturing method according to a ninth embodiment for thefilm 22 having negative fixed charges used in the manufacturing methods(the first manufacturing methods) for a solid-state imaging deviceaccording to the first to fifth embodiments is explained below withreference to FIG. 37. In FIG. 37, as an example, the manufacturingmethod is applied the first manufacturing method according to the firstembodiment. A method of forming a film having negative fixed chargesaccording to this embodiment can be applied to the methods of forming afilm having negative fixed charges of the first manufacturing methodsaccording to the second to fifth embodiments as well. In thisexplanation, as an example of a film having negative fixed charges, ahafnium oxide film is used.

Although not shown in (1) in FIG. 37, pixel separation areas, thelight-receiving section 12, transistors, and the like are formed in thesemiconductor substrate (or the semiconductor layer) 11. For example, awiring layer 63 is formed on a rear surface side of the semiconductorsubstrate 11. The wiring layer 63 includes wiring 61 and an insulatingfilm 62 that covers the wiring 61.

The film 21 for reducing interface state density is formed on thesemiconductor substrate 11. The film 21 for reducing interface statedensity is formed by, for example, a silicon oxide (SiO₂) film 21Si.

As the semiconductor substrate 11, for example, a monocrystal siliconsubstrate is used. The semiconductor substrate 11 is formed in thethickness of about 3 μm to 5 μm.

As shown in (2) in FIG. 37, a hafnium oxide (HfO₂) film 22Hf is formedon the silicon oxide (SiO₂) film 21Si as the film 22 having negativefixed charges. Consequently, a hole accumulation layer is formed on thelight-receiving surface side of the light-receiving section 12.

Therefore, at least on the light-receiving section 12, the film 21 forreducing interface state density needs to be formed, by the hafniumoxide film 22Hf, in thickness enough for forming a hole accumulationlayer on the light-receiving surface 12 s side of the light-receivingsection 12. The film thickness is, for example, equal to or larger thanone atom layer and equal to or smaller than 100 nm. As an example, thefilm 21 for reducing interface state density is formed in the thicknessof 30 nm. A function of a reflection preventing film can be imparted tothis silicon oxide film.

In the film formation of the hafnium oxide film 22Hf, for example, theatomic layer deposit method is used. In this film formation, thesemiconductor substrate 11, the wiring layer 63, and the like need to beheld at the temperature equal to or lower than 400° C. This is for thepurpose of securing reliability of a diffusion area and wiring formed inthe wiring layer 63, the semiconductor device 11, and the like.

Since film formation temperature is held at the temperature equal to orlower than 400° C., the hafnium oxide film 22Hf is formed in anamorphous state.

As shown in (3) in FIG. 37, light irradiation treatment for irradiatinglight L on the surface of the hafnium oxide film 22Hf is performed tocrystallize the amorphous hafnium oxide film 22Hf.

For example, according to condition setting under which the temperatureof the surface of a hafnium oxide film was set to be equal to or higherthan 1400° C. when light having the wavelength of 528 nm was irradiatedfor 120 ns, 140 ns, 160 ns, and 200 ns, a temperature distribution in adepth direction from the surface of the hafnium oxide film wascalculated by simulation. A result of the simulation is shown in FIG.38.

In FIG. 38, the ordinate indicates temperature and the abscissaindicates depth from the surface of the hafnium oxide film.

As shown in FIG. 38, it was found that, with the irradiation time of 120ns to 200 ns, an area having the temperature equal to or lower than 400°C. was an area deeper than 3 μm.

For example, according to condition setting under which the temperatureof the surface of a hafnium oxide film was set to be equal to or higherthan 1400° C. when light having the wavelength of 528 nm was irradiatedfor 800 ns, 1200 ns, and 1600 ns, a temperature distribution in a depthdirection from the surface of the hafnium oxide film was calculated bysimulation. A result of the simulation is shown in FIG. 39.

In FIG. 39, the ordinate indicates temperature and the abscissaindicates depth from the surface of the hafnium oxide film.

As shown in FIG. 39, it was found that, with the irradiation time of 800ns to 1200 ns, an area having the temperature equal to or lower than400° C. was an area deeper than 3

According to a simulation result, irradiation time needs to be equal toor shorter than 1200 ns for light irradiation to set the temperature ofthe surface of the hafnium oxide film 22Hf formed on the surface side ofthe semiconductor substrate 11 via the silicon oxide film 21Si to beequal to or higher than 1400° C. and the temperature of the wiring layer63 formed on the rear surface side of the semiconductor substrate 11 tobe equal to or lower than 400° C.

Therefore, in the light irradiation treatment, light irradiation time ispreferably set to be equal to or shorter than 1 ms. It is seen that atemperature difference between the wiring layer 63 and the surface ofthe hafnium oxide film 22Hf is larger as the irradiation time isshorter.

According to the simulation result, a condition for efficiently using,for crystallization of the hafnium oxide film 22Hf, light irradiated tokeep the wiring layer 63 at the temperature equal to or lower than 400°C. and heating and crystallizing the hafnium oxide film 22Hf waschecked.

Light having wavelength, penetration length “d” of which into thesemiconductor substrate 11 of monocrystal silicon is equal to or smallerthan 3 μm, is used. The penetration length “d” is defined as d=λ/(4πk).

When the light is irradiated, absorption of the light and heatgeneration occur in a portion near the silicon oxide film 21Si in thesemiconductor substrate 11 of monocrystal silicon. The hafnium oxidefilm 22Hf is heated by heat conduction from the semiconductor substrate11 side and crystallized. The irradiated light does not reach a portionnear the wiring layer 63 in the semiconductor substrate 11 ofmonocrystal silicon. Therefore, the temperature of the wiring layer 63can be kept low, for example, at the temperature equal to or lower than400° C., preferably, equal to or lower than 200° C.

As an example, when the light has the wavelength λ of 527 nm, theextinction coefficient “k” of the hafnium oxide film 22Hf is 0, theextinction coefficient “k” of silicon oxide is 0, and the extinctioncoefficient “k” of silicon is 0.03. Therefore, there is no loss of theincident light in the hafnium oxide film 22Hf and the silicon oxide film21Si.

On the other hand, there is a loss of the incident light in thesemiconductor substrate 11 of monocrystal silicon. Since the penetrationlength of the light d=λ/(4πk) is 1.3 μm, when it is assumed that thethickness of the semiconductor substrate 11 of monocrystal silicon is 5μm, the influence of the irradiated light can be neglected in the wiringlayer 63. In a simulation taking into account heat conduction, as in thesimulation described above, when the penetration length “d” is equal toor smaller than 5% μm, the temperature of the wiring layer 63 is equalto or lower than 200° C.

In a sample of the hafnium oxide film 22Hf formed in the thickness of2.5 nm, when a pulse laser beam having the wavelength λ of 527 nm wasirradiated for irradiation time of 150 ns, crystallization of thehafnium oxide film 22Hf could be confirmed.

Alternatively, light having wavelength, penetration length “d” of whichinto the hafnium oxide film 22Hf is equal to or smaller than 60 nm, isused as light irradiated in order to keep the wiring layer 63 at thetemperature equal to or lower than 400° C. and heat and crystallize thehafnium oxide film 22Hf. The penetration length “d” is defined asd=λ/(4πk).

Since most of the irradiated light is absorbed by the hafnium oxide film22Hf, light entering the semiconductor substrate 11 of monocrystalsilicon can be reduced.

Even if there is some heat conduction from the hafnium oxide film 22Hfor the silicon oxide film 21Si to the semiconductor substrate 11 ofmonocrystal silicon, the temperature of the wiring layer 63 can be keptlow.

As an example, when the irradiated light has the wavelength λ of 200 nm,if the refractive index “n” of the hafnium oxide film 22Hf is set to 2.3(the extinction coefficient “k” is set to 0.3), the refractive index “n”of the silicon oxide film 21Si is set to 1.5, and the refractive index“n” of monocrystal silicon is set to 0.9, there is a loss of incidentlight in the hafnium oxide film 22Hf and the silicon oxide film 21Si andthe penetration length of light d=λ/(4πk) is 53 nm. Therefore, it ispossible to reduce light passing through the hafnium oxide film 22Hf ifthe thickness of the hafnium oxide film 22Hf is set to 60 nm.

It is efficient to optimize the thickness “t” of the silicon oxide film21Si using the principle of interference such that more light isconcentrated on the hafnium oxide film 22Hf. An example of desirablethickness “t” of the silicon oxide film 21Si at the refractive indexdescribed above is λ/2n=66 nm (n is the refractive index of siliconoxide).

A relation among the refractive indexes of the respective films thatcondense the light irradiated on the hafnium oxide film 22Hf isexplained with reference to a sectional view of a schematicconfiguration in FIG. 40.

As shown in FIG. 40, the refractive index of a medium 1 is representedas n₁, the refractive index of a medium 2 is represented as n₂, and therefractive index of a medium 3 is represented as n₃.

To cause lights irradiated on the medium 1 to intensity each other inthe medium 1, in a relation of n₁>n₂>n₃ or n₁<n₂<n₃, the thickness “t”of the medium 2 is (λ/2n₂)_(m) (m is a natural number) according to aninterference condition.

In a relation of n₁<n₂>n₃ or n₁>n₂<n₃, the thickness “t” of the medium 2is λ/4n₂+(λ/2n₂)_(m) (m is a natural number).

When light having the wavelength λ of 200 nm is used as irradiatedlight, if it is assumed that the medium 1 is the hafnium oxide film22Hf, the medium 2 is a silicon oxide film, and the medium 3 is thesemiconductor substrate 11 of monocrystal silicon, since n₁>n₂>n₃,desired thickness “t” of the silicon oxide film 21Si is (λ/2n₂)_(m),(m=1), =66 nm.

In this way, it is preferable to select the thickness of the siliconoxide film 21Si such that light is condensed on the hafnium oxide film22Hf.

As explained above, in order to change the hafnium oxide film 22Hf inthe non-crystal state to a hafnium oxide film in the crystal state, itis preferable to perform light irradiation in extremely short time equalto or shorter than 1 ms. The irradiation time of light is set to beequal to or smaller than 1 ms because, if the irradiation time is long,the temperature of the wiring layer 63 is raised by the heat conductionof the semiconductor substrate 11 of monocrystal silicon and it isdifficult to heat only the hafnium oxide film 22Hf.

Thereafter, formation of a rear side electrode, formation of a colorfilter layer, formation of a condensing lens (an on-chip lens), and thelike are performed.

In the explanation of the ninth embodiment, the examples of thewavelength of the light used for light irradiation are 528 nm and 200nm. However, the wavelength of light that can be used for lightirradiation is not limited to these wavelengths. It is possible to useultraviolet rays including a far ultraviolet ray to a near ultravioletray, visible rays, and infrared rays including a near infrared ray to aninfrared ray. In the case of the infrared ray including the infrared rayto the far infrared ray, it is necessary to set the irradiation time toextremely short time of about several tens ns and increase power.

A solid-state imaging device (a second solid-state imaging device)according to the first embodiment is explained with reference to asectional view of a main part configuration in FIG. 41. In FIG. 41, alight shielding film that shields a part of a light-receiving sectionand a peripheral circuit section, a color filter layer that splits lightmade incident on the light-receiving section, a condensing lens thatcondenses the incident light on the light-receiving section, and thelike are not shown.

As shown in FIG. 41, a solid-state imaging device 6 has, in thesemiconductor substrate (or the semiconductor layer) 11, thelight-receiving sections 12 that photoelectrically convert incidentlight and has, on a side of the light-receiving sections 12, theperipheral circuit section 14 in which peripheral circuits (e.g., thecircuit 14C) is formed via the pixel separation area 13. An insulatingfilm 27 is formed on the light-receiving surfaces 12 s of thelight-receiving sections (including the hole accumulation layers 23explained later) 12. The insulating film 27 is formed by, for example, asilicon oxide (SiO₂) film. A film 28 that suppress negative voltage isformed on the insulating film 27.

In the figure, the insulating film 27 is formed to be thicker on theperipheral circuit section 14 than on the light-receiving sections 12such that a distance from the surface of the peripheral circuit section14 to the film 28 is longer than a distance from the surfaces of thelight-receiving sections 12 to the film 28.

When the insulating film 27 is formed by, for example, the silicon oxidefilm, on the light-receiving sections 12, the insulating film 27 has aneffect same as that of the film 21 for reducing interface state densityexplained above. Therefore, the insulating film 27 on thelight-receiving sections 12 is preferably formed in the thickness, forexample, equal to or larger than one atom layer and equal to or smallerthan 100 nm.

Consequently, when negative voltage is applied to the film 28 to whichnegative voltage is applied, the hole accumulation layers 23 are formedon the light-receiving surfaces side of the light-receiving sections 12.

In the peripheral circuits of the peripheral circuit section 14, forexample, when the solid-state imaging device 6 is a CMOS image sensor,there is a pixel circuit including transistors such as a transfertransistor, a reset transistor, an amplification transistor, and aselection transistor.

The peripheral circuits include a driving circuit that performs anoperation for reading out a signal in a readout row of a pixel arraysection including the plural light-receiving sections 12, a verticalscanning circuit that transfers the read-out signal, a shift register oran address decoder, and a horizontal scanning circuit as well.

In the peripheral circuits of the peripheral circuit section 14, forexample, when the solid-state imaging device 6 is a CCD image sensor,there are a readout gate that reads out photoelectrically-convertedsignal charges from a light-receiving section to a vertical transfergate, a vertical-charge transfer section that transfers the read-outsignal charges in a vertical direction. The peripheral circuits includea horizontal-charge transfer section as well.

The film 28 to which negative voltage is applied is formed by, forexample, a film having conductivity transparent to incident light, forexample, a conductive film transparent to visible light. As such a film,an indium tin oxide film, an indium zinc oxide film, an indium oxidefilm, a tin oxide film, a gallium zinc oxide film, and the like can beused.

On the film 28 to which negative voltage is applied in the solid-stateimaging device 6, a light shielding film that shields a part of thelight-receiving sections 12 and the peripheral circuit section 14, acolor filter layer that splits light made incident on at least thelight-receiving sections 12, a condensing lens that condenses theincident light on the light-receiving sections 12, and the like areprovided. As an example, as the configuration, the configuration ofanyone of the solid-state imaging devices 1, 2, and 3 can also beapplied.

In the solid-state imaging device (the second solid-state imagingdevice) 6, since the film 28 to which negative voltage is applied isformed on the insulating film 27 formed on the light-receiving surfaces12 s of the light-receiving sections 12, hole accumulation layers aresufficiently formed in interfaces on the light-receiving surfaces 12 sside of the light-receiving sections 12 by an electric field generatedwhen negative voltage is applied to the film 28 to which negativevoltage is applied.

Therefore, the generation of charges (electrons) from the interfaces issuppressed. Even if charges (electrons) are generated, since the chargesflows in the hole accumulation layers 23 in which a large number ofholes are present without flowing into charge accumulation portionsforming wells of potential in the light-receiving sections, the charges(the electrons) can be eliminated.

Therefore, it is possible to prevent the charges due to the interfacesfrom changing to dark currents to be detected by the light-receivingsections 12 and suppress the dark currents due to the interface statedensity.

Moreover, since the insulating film 27 functioning as a film forreducing interface state density is formed on the light-receivingsurfaces 12 s of the light-receiving sections 12, the generation ofelectrons due to interface state density is further suppressed.Therefore, electrons due to interface state density are prevented fromflowing into the light-receiving sections 12 as dark currents.

As shown in the figure, a distance from the surface of the peripheralcircuit section 14 to the film 28 to which negative voltage is appliedis formed larger than a distance from the surface of the light-receivingsections 12 to the film 28 by the insulating film 27. Therefore, anelectric field generated when negative voltage is applied to the film 28is prevented from affecting the peripheral circuit section 14. Thismakes it possible to eliminate a malfunction of the circuits in theperipheral circuit section 14.

A solid-state imaging device (a second solid-state imaging device)according to the second embodiment is explained with reference to asectional view of a main part configuration in FIG. 42. In FIG. 42, alight shielding film that shields a part of a light-receiving sectionand a peripheral circuit section, a color filter layer that splits lightmade incident on the light-receiving section, a condensing lens thatcondenses the incident light on the light-receiving section, and thelike are not shown.

As shown in FIG. 42, in a solid-state imaging device 7, the film 25 forseparating a film to which negative voltage is applied and alight-receiving surface is formed on the peripheral circuit section 14,substantially, between the insulating film 27 and the film 28 to whichnegative voltage is applied in the solid-state imaging device 6. Thefilm 25 desirably has positive fixed charges to cancel the influence ofthe negative voltage. The film 25 is hereinafter referred to as filmhaving positive fixed charges.

The film 25 having positive fixed charges only has to be formed betweenthe peripheral circuit section 14 and the film 28 to which negativevoltage is applied and may be formed on the insulating film 27 or underthe insulating film 27.

In the figure, the insulating film 27 is formed by a film having uniformthickness. However, as in the solid-state imaging device 6, theinsulating film 27 may be an insulating film having larger thickness onthe peripheral circuit section 14 than on the light-receiving section12.

As an example of the film 25 having positive fixed charges, there is asilicon nitride film.

Since the film 25 having positive fixed charges is formed between theperipheral circuit section 14 and the film 28 to which negative voltageis applied, a negative electric field generated when negative voltage isapplied to the film 28 to which negative voltage is applied is reducedby the positive fixed charges in the film 25 having positive fixedcharges. Therefore, the peripheral circuit 14 is not affected by thenegative electric field.

Therefore, a malfunction of the peripheral circuit section 14 due to thenegative electric field can be prevented. This improves reliability ofthe peripheral circuit section 14.

As described above, the configuration in which the film 25 havingpositive fixed charges is formed between the peripheral circuit section14 and the film 28 to which negative voltage is applied can be appliedto the solid-state imaging device 6 as well. Effects same as those ofthe solid-state imaging device 7 can be obtained.

A manufacturing method (a second manufacturing method) for a solid-stateimaging device according to the first embodiment is explained withreference to sectional views of a manufacturing process showing a mainpart in FIG. 43 to FIG. 45. In FIG. 43 to FIG. 45, as an example, amanufacturing process for the solid-state imaging device 6 is shown.

As shown in (1) in FIG. 43, the light-receiving sections 12 thatphotoelectrically convert incident light, the pixel separation areas 13that separate the light-receiving sections 12, the peripheral circuitsection 14 in which peripheral circuits (e.g., a circuit 14C) are formedwith respect to the light-receiving section 12 via the pixel separationarea 13, and the like are formed in the semiconductor substrate (or thesemiconductor layer) 11. An existing manufacturing method is used forthe manufacturing method. An insulating film 29 having permeability tothe incident light is formed. The insulating film 29 is formed by, forexample, a silicon oxide film.

As shown in (2) in FIG. 43, a resist mask 53 is formed on the insulatingfilm 29 above the peripheral circuit section 14 by the resistapplication and the lithography technique.

As shown in (3) in FIG. 44, the insulating film 29 is etched by usingthe resist mask 53 (see (2) in FIG. 43) to leave the insulating film 29on the peripheral circuit section 14. Thereafter, the resist mask 53 isremoved.

As shown in (4) in FIG. 44, the film 21 for reducing interface statedensity that covers the insulating film 26 is formed on thelight-receiving surfaces 12 s of the light-receiving sections 12,actually, on the semiconductor substrate 11. The film 21 for reducinginterface state density is formed by, for example, a silicon oxide(SiO₂) film. Consequently, the insulating film 27 is formed by theinsulating film 29 and the film 21 for reducing interface state density.

As shown in FIG. 45, the film 28 to which negative voltage is applied isformed on the film 21 for reducing interface state density. Whennegative voltage is applied to the film 28 to which negative voltage isapplied, the hole accumulation layers 23 are formed on thelight-receiving surfaces side of the light-receiving sections 12.

Therefore, at least on the light-receiving sections 12, the film 21 forreducing interface state density needs to be formed, by the negativevoltage applied to the film 28 to which negative voltage is applied, inthickness enough for forming the hole accumulation layers 23 on thelight-receiving surfaces 12 s side of the light-receiving sections 12.The film thickness is, for example, equal to or larger than one atomlayer and equal to or smaller than 100 nm.

The film 28 to which negative voltage is applied is formed by, forexample, a film having conductivity transparent to incident light, forexample, a conductive film transparent to visible light. As such a film,an indium tin oxide film, an indium zinc oxide film, an indium oxidefilm, a tin oxide film, a gallium zinc oxide film, and the like can beused.

On the film 28 to which negative voltage is applied in the solid-stateimaging device 6, a light shielding film that shields a part of thelight-receiving sections 12 and the peripheral circuit section 14, acolor filter layer that splits light made incident on at least thelight-receiving sections 12, a condensing lens that condenses theincident light on the light-receiving sections 12, and the like areformed.

As a manufacturing method therefor, as an example, any one of themethods (the first manufacturing methods) for a solid-state imagingdevice according to the embodiments described above can also be used.

In the manufacturing method (the second manufacturing method) for thesolid-state imaging device 6, the film 28 to which negative voltage isapplied is formed on the insulating film 27 formed on thelight-receiving surfaces 12 s of the light-receiving sections 12.Therefore, the hole accumulation layers 23 are sufficiently formed inthe interfaces on the light-receiving surfaces 12 s side of thelight-receiving sections 12 by an electric field generated when negativevoltage is applied to the film 28 to which negative voltage is applied.

Therefore, charges (electrons) generated from the interfaces can besuppressed. Even if charges (electrons) are generated from theinterfaces, since the charges (electrons) flow in the hole accumulationlayers 23 in which a large number of holes are present without flowinginto charge accumulation portions forming wells of potential in thelight-receiving sections 12, the charges (the electrons) can beeliminated.

Therefore, it is possible to prevent the charges due to interfaces fromchanging to dark currents to be detected by the light-receiving sections12. Dark currents due to interface state density are suppressed.

Moreover, since the film 21 for reducing interface state density isformed on the light-receiving surfaces 12 s of the light-receivingsections 12, the generation of electrons due to the interface statedensity is further suppressed. Therefore, the electrons due to theinterface state density are prevented from flowing into thelight-receiving sections 12 as dark currents.

As shown in the figure, a distance from the surface of the peripheralcircuit section 14 to the film 28 to which negative voltage is appliedis formed larger than a distance from the surfaces of thelight-receiving sections 12 to the film 28 and the thickness of theinsulating film 27 on the peripheral circuit section 14 is formed largerthan the thickness of the insulating film 27 on the light-receivingsections 12 by the insulating film 27.

Therefore, an electric field generated when negative voltage is appliedto the film 28 is prevented from affecting the peripheral circuitsection 14. In other words, since field intensity is reduced and holesare prevented from being accumulated on the surface of the peripheralcircuit section 14, it is possible to eliminate a malfunction of thecircuits in the peripheral circuit section 14.

A manufacturing method (a second manufacturing method) for a solid-stateimaging device according to the second embodiment is explained withreference to sectional views of a manufacturing process showing a mainpart in FIG. 46 to FIG. 47. In FIG. 46 to FIG. 47, as an example, amanufacturing process for the solid-state imaging device 7 is shown.

As shown in (1) in FIG. 46, the light-receiving sections 12 thatphotoelectrically convert incident light, the pixel separation areas 13that separate the light-receiving sections 12, the peripheral circuitsection 14 in which peripheral circuits (e.g., a circuit 14C) are formedwith respect to the light-receiving section 12 via the pixel separationarea 13, and the like are formed in the semiconductor substrate (or thesemiconductor layer) 11. An existing manufacturing method is used forthe manufacturing method. The insulating film 27 having permeability tothe incident light is formed. The insulating film 27 is formed by, forexample, a silicon oxide film. Moreover, the film 25 having positivefixed charges is formed on the insulating film 27. The film 25 havingpositive fixed charges is formed by, for example, a silicon nitridefilm.

As shown in (2) in FIG. 46, a resist mask 54 is formed on the film 25having positive fixed charges above the peripheral circuit section 14 bythe resist application and the lithography technique.

As shown in (3) in FIG. 47, the film 25 having positive fixed charges isetched by using the resist mask 54 (see (2) in FIG. 46) to leave thefilm 25 having positive fixed charges on the peripheral circuit section14. Thereafter, the resist mask 54 is removed.

As shown in (4) in FIG. 47, the film 28 to which negative voltage isapplied is formed on the insulating film 27 and the film 25 havingpositive fixed charges. When negative voltage is applied to the film 28to which negative voltage is applied, the hole accumulation layers 23are formed on the light-receiving surfaces side of the light-receivingsections 12. It is possible to cause the insulating film 27 to functionas a film for reducing interface state density.

Therefore, at least on the light-receiving sections 12, the insulatingfilm 27 needs to be formed, by the negative voltage applied to the film28 to which negative voltage is applied, in thickness enough for formingthe hole accumulation layers on the light-receiving surfaces 12 s sideof the light-receiving sections 12. The film thickness is, for example,equal to or larger than one atom layer and equal to or smaller than 100nm.

The film 28 to which negative voltage is applied is formed by, forexample, a film having conductivity transparent to incident light, forexample, a conductive film transparent to visible light. As such a film,an indium tin oxide film, an indium zinc oxide film, an indium oxidefilm, a tin oxide film, a gallium zinc oxide film, and the like can beused.

On the film 28 to which negative voltage is applied in the solid-stateimaging device 7, a light shielding film that shields a part of thelight-receiving sections 12 and the peripheral circuit section 14, acolor filter layer that splits light made incident on at least thelight-receiving sections 12, a condensing lens that condenses theincident light on the light-receiving sections 12, and the like areformed.

As a manufacturing method therefor, as an example, any one of themanufacturing methods (the first manufacturing methods) for asolid-state imaging device explained above can also be used.

In the manufacturing method (the second manufacturing method) for thesolid-state imaging device 7, the film 28 to which negative voltage isapplied is formed on the insulating film 27 formed on thelight-receiving surfaces 12 s of the light-receiving sections 12.Therefore, the hole accumulation layers 23 are sufficiently formed inthe interfaces on the light-receiving surfaces 12 s side of thelight-receiving sections 12 by an electric field generated when negativevoltage is applied to the film 28 to which negative voltage is applied.

Therefore, charges (electrons) generated from the interfaces can besuppressed. Even if charges (electrons) are generated from theinterfaces, since the charges (electrons) flow in the hole accumulationlayers 23 in which a large number of holes are present without flowinginto charge accumulation portions forming wells of potential in thelight-receiving sections 12, the charges (the electrons) can beeliminated.

Therefore, it is possible to prevent the charges due to interfaces fromchanging to dark currents to be detected by the light-receiving sections12. Dark currents due to interface state density are suppressed.

Moreover, since the film 21 for reducing interface state density isformed on the light-receiving surfaces 12 s of the light-receivingsections 12, the generation of electrons due to the interface statedensity is further suppressed. Therefore, the electrons due to theinterface state density are prevented from flowing into thelight-receiving sections 12 as dark currents.

Since the film 25 having positive fixed charges is formed between theperipheral circuit section 14 and the film 28 to which negative voltageis applied, a negative electric field generated when negative voltage isapplied to the film 28 to which negative voltage is applied is reducedby the positive fixed charges in the film 25 having positive fixedcharges. Therefore, the peripheral circuit 14 is not affected by thenegative electric field.

Therefore, a malfunction of the peripheral circuit section 14 due to thenegative electric field can be prevented. The configuration in which thefilm 25 having positive fixed charges is formed between the peripheralcircuit section 14 and the film 28 to which negative voltage is appliedas described above can be applied to the solid-state imaging device 6 aswell. Effects same as those in the solid-state imaging device 7 can beobtained.

A solid-state imaging device (a third solid-state imaging device)according to an embodiment of the present invention is explained withreference to a sectional view of a main part configuration in FIG. 48.In FIG. 48, a light-receiving section is mainly shown. A peripheralcircuit section, a wiring layer, a light shielding film that shieldsapart of the light-receiving section and a peripheral circuit section, acolor filter layer that splits light made incident on thelight-receiving section, a condensing lens that condenses the incidentlight on the light-receiving section, and the like are not shown.

As shown in FIG. 48, a solid-state imaging device 8 has, in thesemiconductor substrate (or the semiconductor layer) 11, thelight-receiving section 12 that photoelectrically converts incidentlight. An insulating film 31 is formed on the light-receiving surface 12s side of the light-receiving section 12. The insulating film 31 isformed by, for example, a silicon oxide (SiO₂) film.

A film 32 having a value of a work function larger than that of theinterface on the light-receiving surface 12 s side of thelight-receiving section 12 that photoelectrically converts incidentlight (hereinafter referred to as hole accumulation auxiliary film) isformed on the insulating film 31. The hole accumulation layer 23 isformed according to a difference between work functions. The holeaccumulation auxiliary film 32 does not need to be electricallyconnected to other elements and wiring. Therefore, the hole accumulationauxiliary film 32 may be an insulating film or a film havingconductivity such as a metal film.

For example, a wiring layer 63 including the wiring 61 in plural layersand the insulating film 62 is formed on the opposite side of the lightincidence side of the semiconductor substrate 11 in which thelight-receiving section 12 is formed. The wiring layer 63 is supportedby a supporting substrate 64.

For example, since the hole accumulation layer 23 is formed of silicon(Si), a value of a work function thereof is about 5.1 eV. Therefore, thehole accumulation auxiliary film 32 only has to be a film having a valueof the work function larger than 5.1.

For example, when a metal film is used, according to chronologicalscientific tables, a value of a work function of an iridium (110) filmis 5.42, a value of a work function of an iridium (111) film is 5.76, avalue of a work function of a nickel film is 5.15, a value of a workfunction of a palladium film is 5.55, a value of a work function of anosmium film is 5.93, a value of a work function of a gold (100) film is5.47, a value of a work function of a gold (110) film is 5.37, and avalue of a work function of a platinum film is 5.64. These films can beused for the hole accumulation auxiliary film 32.

Besides these films, any metal film can be used for the holeaccumulation auxiliary film 32 as long as the metal film has a value ofa work function larger than that of the interface on the light-receivingsurface 12 s of the light-receiving section 12. A value of a workfunction of an ITO (In₂O₃) used as a transparent electrode is set to 4.8eV. However, a work function of an oxide semiconductor can be controlledby a film forming method and the introduction of impurities.

The hole accumulation auxiliary film 32 is formed on the light-incidenceside. Therefore, it is important to form the hole accumulation auxiliaryfilm 32 in thickness for transmitting incident light. The transmittanceof the incident light is preferably as high as possible. For example,the transmittance equal to or higher than 95% is preferably secured.

The hole accumulation auxiliary film 32 only has to be able to use adifference of work functions between the hole accumulation auxiliaryfilm 32 and the surface of the light-receiving section 12. A lowresistance value thereof is not limited. Therefore, for example, evenwhen a conductive film is used, it is unnecessary to form the conductivefilm thick. For example, when incident light intensity is represented asI₀ and an absorbance index is represented as α(α=(4πk)/λ, “k” is aBoltzmann's constant, and λ is the wavelength of the incident light),light intensity in a depth “z” position is represented by I(z)=I₀exp(−α·z). Therefore, when thickness I(z)/I₀=0.8 is calculated, forexample, the thickness is 1.9 nm for an iridium film, 4.8 nm for a goldfilm, and 3.4 nm for a platinum film. It is seen that, although thethickness is different depending on a film type, the thicknesspreferably only has to be equal to or smaller than 2 nm.

The hole accumulation auxiliary film 32 may be an organic film. Forexample, polysthylenedioxytyiophene can also be used. As describedabove, the hole accumulation auxiliary film 32 may be a conductive film,an insulating film, or a semiconductor film as long as the film has avalue of a work function larger than a value of a work function of theinterface on the light-receiving surface 12 s side of thelight-receiving section 12.

The solid-state imaging device 8 has, on the insulating film 31 formedon the light-receiving section 12, the film (the hole accumulationauxiliary film) 32 having a value of a work function larger than that ofthe interface on the light-receiving surface 12 s side of thelight-receiving section 12. Therefore, hole accumulation efficiency ofthe hole accumulation layer 23 is improved. The hole accumulation layer23 formed in the interface on the light-receiving side of thelight-receiving section 12 can accumulate sufficient holes.Consequently, dark currents are reduced.

An example of a configuration of a solid-state imaging device employingthe hole accumulation auxiliary film 32 is explained with reference toFIG. 49. In FIG. 49, a CMOS image sensor is shown.

As shown in FIG. 49, plural pixel sections 71 having light-receivingsections (e.g., photodiodes) 12 that convert incident light intoelectric signals, a transistor group 65 (a part of which is shown in thefigure) including a transfer transistor, an amplification transistor,and a reset transistor, and the like are formed in the semiconductorsubstrate 11. For example, a silicon substrate is used as thesemiconductor substrate 11. Signal processing sections (not shown) thatprocess signal charges read out from the respective light-receivingsections 12 are also formed.

The pixel separation areas 13 are formed in a part of the periphery ofthe pixel sections 71, for example, among the pixel sections 71 in a rowdirection or a column direction.

The wiring layer 63 is formed on a front side of the semiconductorsubstrate 11 in which the light-receiving sections 12 are formed (in thefigure, a lower side of the semiconductor substrate 11). The wiringlayer 63 includes the wiring 61 and the insulating films 62 that coverthe wiring 61. The supporting substrates 64 are formed in the wiringlayers 63. The supporting substrates 64 are formed by, for example,silicon substrates.

In the solid-state imaging device 1, the hole accumulation layers 23 areformed on the rear surface side of the semiconductor substrate 11. Thehole accumulation auxiliary films 32 explained above are formed on theupper surfaces of the hole accumulation layers 23 via the insulatingfilms 31. Moreover, the organic color filter layers 44 are formed viainsulating films (not shown). The organic color filter layers 44 areformed in association with the light-receiving sections 12. For example,the organic filter layers 44 are formed by arranging organic colorfilters of blue, red, and green in, for example, a checkered pattern.The condensing lenses 45 that condense incident light on the respectivelight-receiving sections 12 are formed on the respective organic colorfilter layers 44.

A manufacturing method (a third manufacturing method) for a solid-stateimaging device according to the first embodiment is explained withreference to a flowchart in FIG. 50, sectional views of a manufacturingprocess in FIG. 51, and sectional views of a manufacturing processshowing a main part in FIG. 52. In FIG. 50 to FIG. 52, as an example, amanufacturing process for the solid-state imaging device 8 is shown.

As shown in (1) in FIG. 50 and (1) in FIG. 51, first, an SOI substrate81 in which a silicon layer 84 is formed on a silicon substrate 82 viaan insulating layer (e.g., a silicon oxide layer) 83 is prepared. A rearsurface mark 85 for alignment is formed in the silicon layer 84.

As shown in (2) in FIG. 50 and (2) in FIG. 51, a pixel separation area(not shown), the hole accumulation layer 23, the light-receiving section12, the transistor group 65, and the wiring layer 63 are formed in thesilicon layer 84 of the SOI substrate 81. The hole accumulation layer 23may be formed in a process after thin-filming of a substrate.

As shown in (3) in FIG. 50 and (3) in FIG. 51, the wiring layer 63 andthe supporting substrate 64 are bonded.

As shown in (4) in FIG. 50 and (4) in FIG. 51, thin-filming of the SOIsubstrate 81 is carried out. The silicon substrate 82 is removed by, forexample, grinding or polishing.

Although not shown in the figure, the hole accumulation layer 23 may beformed by instruction of impurities and activation processing by forminga cap film (not shown) after removing the insulating film 82 of the SOIsubstrate 81. As an example, a plasma-TEOS silicon oxide film is formedas the cap film in the thickness of 30 nm and the introduction ofimpurities is performed by ion implantation of boron. As a condition forthe ion implantation, for example, implantation energy is set to 20 keVand a dosage is set to 1×10¹³/cm².

The activation is preferably performed by annealing at the temperatureequal to or lower than 400° C. that does not destroy the bonding of thewiring layer 63 and the supporting substrate 54. The cap film is removedby, for example, fluoric acid treatment. The insulating layer 83 of theSOI substrate 81 may be removed.

In this way, as shown in (1) in FIG. 52, the interface 23 on thelight-receiving surface side of the light-receiving section is formed onthe light-receiving section 12.

As shown in (2) in FIG. 52, the insulating film 31 is formed on the holeaccumulation layer 23 (on the light incidence side). As an example, aplasma-TEOS silicon oxide film is formed in the thickness of 30 nm.

As shown in (3) in FIG. 52, a film having a value of a work functionlarger than that of the interface on the light-receiving surface 12 sside of the light-receiving section 12 (a value of a work function isabout 5.1 eV), i.e., the hole accumulation auxiliary film 32 is formedon the insulating film 31 (on the light incidence side). As an example,a platinum (Pt) film having a work function of 5.6 eV, which is a metalthin film, is formed in the thickness of 3 nm by sputtering. Candidatesof other metal thin films include iridium (Ir), rhenium (Re), nickel(Ni), palladium (Pd), cobalt (Co), ruthenium (Ru), rhodium (Rh), osmium(Os), and gold (Au). Naturally, alloys can also be used.

A material of the hole accumulation auxiliary film 32 may be an ITO(In₂O₃) because a value of a work function of the interface on thelight-receiving surface side of the light-receiving section is about 5.1eV in this example. The ITO can have a value of a work function of 4.5eV to 5.6 eV in a film formation process therefor. Other oxidesemiconductors such as semiconductors in which RuO₂, SnO₂, IrO₂, OsO₂,ZnO, ReO₂, and MoO₂ and acceptor impurities are introduced andpolysthylenedioxytyiophene (PEDOT) as an organic material can be amaterial of the hole accumulation auxiliary film 32 because the oxidesemiconductors can have a value of a work function larger than 5.1 eV.Examples of a film forming method at the temperature equal to or lowerthan 400° C. include ALD, CVD, and vapor doping.

As shown in (5) in FIG. 50 and (5) in FIG. 51, a rear surface electrode92 is formed via a barrier metal 91.

As shown in (6) in FIG. 50 and (6) in FIG. 51, above the light-receivingsection 12, the color filter layer 44 is formed and, then, thecondensing lens 45 is formed. In this way, the solid-state imagingdevice 8 is formed.

In the manufacturing method (the third manufacturing method) for asolid-state imaging device, the film having a value of a work functionlarger than that of the interface on the light-receiving surface 12 sside of the light-receiving section 12, i.e., the hole accumulationauxiliary film 32 is formed on the insulating film 31 formed on thelight-receiving section 12. Therefore, hole accumulation efficiency ofthe hole accumulation layer 23 is improved. The hole accumulation layer23 formed in the interface on the light-receiving surface 12 s side ofthe light-receiving section 12 can accumulate sufficient holes.Consequently, dark currents are reduced.

The hole accumulation auxiliary film 32 only has to be a film that has avalue of a work function larger than a value of a work function of thehole accumulation layer 23. Since it is unnecessary to feed an electriccurrent through the hole accumulation auxiliary film 32, the holeaccumulation layer may be a conductive film, an insulating film, or asemiconductor film. Therefore, a material having high resistance may beselected for the hole accumulation auxiliary film 32.

An external signal input terminal is also unnecessary for the holeaccumulation auxiliary film 32.

The solid-state imaging devices 1 to 8 according to the embodiments canbe applied to a back illuminated solid-state imaging device includingplural pixel sections having light-receiving sections that convertincident light amounts into electric signals and a wiring layer on onesurface side of a semiconductor substrate in which the respective pixelsections are formed, wherein light made incident from the opposite sideof the surface on which the wiring layer is formed is received by therespective light-receiving sections. Naturally, the solid-state imagingdevices 1 to 8 according to the embodiments can also be applied to afront illuminated solid-state imaging device in which a wiring layer isformed on a light-receiving surface side and an optical path of incidentlight made incident on light-receiving sections is formed as anon-formation area of the wiring layer not to block the incident lightmade incident on the light-receiving sections.

An imaging apparatus according to an embodiment of the present inventionis explained with reference to a block diagram of FIG. 53. Examples ofthe imaging apparatus include a video camera, a digital still camera,and a camera of a cellular phone.

As shown in FIG. 53, an imaging apparatus 500 includes a solid-stateimaging device (not shown) in an imaging unit 501. A focusing opticalsystem 502 that focuses an image is provided on a light condensing sideof the imaging unit 501. A signal processing unit 503 including adriving circuit that drives the imaging unit 501 and a signal processingcircuit that processes a signal photoelectrically converted by thesolid-state imaging device into an image is connected to the imagingunit 501. The image signal processed by the signal processing unit 503can be stored by an image storing unit (not shown). In such an imagingdevice 500, the solid-state imaging devices 1 to 8 explained in theembodiments can be used as the solid-state imaging device.

In the imaging apparatus 500 according to this embodiment, thesolid-state imaging device 1 or the solid-state imaging device 2according to the embodiment of the present invention or the solid-stateimaging device having the condensing lens, in which the reflective filmis formed, shown in FIG. 4 is used. Therefore, as explained above, sincethe solid-state imaging device that can improve color reproducibilityand resolution is used, there is an advantage that the imaging apparatus500 can record a high-definition video.

The imaging apparatus 500 according to this embodiment is not limited tothe configuration described above. The imaging apparatus 500 can beapplied to an imaging apparatus of any configuration as long as thesolid-state imaging device is used.

The solid-state imaging devices 1 to 8 may be formed as one chip or maybe a module-like form having an imaging function in which an imagingunit, a signal processing unit, and an optical system are collectivelypackaged.

The present invention can be applied not only to a solid-state imagingdevice but also to an imaging apparatus. When the present invention isapplied to the imaging apparatus, the imaging apparatus can obtain aneffect of high image quality. The imaging apparatus indicates, forexample, a camera and a portable apparatus having an imaging function.“Imaging” includes not only capturing of an image during normal cameraphotographing but also fingerprint detection and the like in a broadersense.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations, and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

What is claimed is:
 1. A method of manufacturing a solid-state imagingdevice comprising: forming a first film having negative fixed chargesover a semiconductor substrate using an atomic layer deposition method;and forming a second film having negative fixed charges on the firstfilm using a physical vapor deposition method, wherein, a holeaccumulation layer is formed on a light-receiving surface side of thesemiconductor substrate by at least one of the first film and the secondfilm.
 2. The method of claim 1, wherein the first and the second filmsare made of hafnium oxide film.
 3. The method of claim 2, wherein thefirst film is formed to have a thickness equal to or larger than 3 nm.4. The method of claim 1, wherein the first and the second films aremade of at least one material selected from the group consisting ofhafnium oxide, aluminum oxide, a zirconium oxide, tantalum oxide,titanium oxide, lanthanum oxide, praseodymium oxide, cerium oxide,neodymium oxide, promethium oxide, samarium oxide, europium oxide,gadolinium oxide, terbium oxide, dysprosium oxide, holmium oxide, erbiumoxide, thulium oxide, ytterbium oxide, lutetium oxide, yttrium oxide,hafnium nitride, aluminum nitride, hafniumoxide nitride and aluminumoxide nitride.
 5. The method of claim 1, wherein an insulating film isformed between the first film and the light receiving surface.
 6. Themethod of claim 5, where the insulating film is a silicon oxide film. 7.The method of claim 5, wherein the insulating film is simultaneouslyformed with the first film.
 8. The method of claim 6, wherein theinsulating film is approximately 1 nm thick.
 9. The method of claim 1,wherein the first and second films are, in combination, from one atomlayer to 100 nm inclusive thick.
 10. A method of manufacturing asolid-state imaging device comprising: forming an insulating film on asemiconductor substrate; forming an amorphous hafnium oxide film on theinsulating film; and applying light irradiation treatment to a surfaceof the amorphous hafnium oxide film to crystallize the hafnium oxidefilm.
 11. A method of manufacturing an imaging apparatus including animaging section and a signal processing section connected to the imagingsection, comprising: forming a first film having negative fixed chargesover a semiconductor substrate with an atomic layer deposition method;and forming a second film having negative fixed charges on the firstfilm with a physical vapor deposition method, wherein, a holeaccumulation layer is formed on a light-receiving surface side of thesemiconductor substrate by at least one of the first film and the secondfilm.
 12. The method of claim 11, wherein the first and the second filmsare made of hafnium oxide film.
 13. The method of claim 12, wherein thefirst film is formed in at least thickness equal to or larger than 3 nm.14. The method of claim 11, wherein the first and the second films aremade of at least one material selected from the group consisting ofhafnium oxide, aluminum oxide, a zirconium oxide tantalum oxide,titanium oxide, lanthanum oxide,praseodymium oxide, cerium oxide,neodymium oxide, promethium oxide, samarium oxide,europium oxide,gadolinium oxide, terbium oxide, dysprosium oxide, holmium oxide,erbiumoxide, thulium oxide, ytterbium oxide,lutetium oxide, yttriumoxide,hafnium nitride, aluminum nitride,hafniumoxide nitride andaluminum oxide nitride.
 15. The method of claim 11, wherein aninsulating film is formed between the first film and the light-receivingsurface.
 16. The method of claim 15, wherein the insulating film is asilicon oxide film.
 17. The method of claim 15, wherein the insulatingfilm is simultaneously formed with the first film.
 18. The method ofclaim 16, wherein the thickness of the insulating film is approximately1 nm.
 19. The method of claim 11, wherein the thickness of the first andsecond films is equal to or larger than one atom layer and equal to orsmaller than 100 nm.
 20. The method of claim 11, wherein the imagingapparatus is one of a video camera, a digital still camera, and a cameraof a mobile phone.